Category: Ransomware

Ryuk, Exploring the Human Connection

In collaboration with Bill Siegel and Alex Holdtman from Coveware.   At the beginning of 2019, McAfee ATR published an article describing how the hasty attribution of Ryuk ransomware to North Korea was missing the point. Since then, collective industry peers discovered additional technical details on Ryuk’s inner workings, the overlap between Ryuk and Hermes2.1, […]

The post Ryuk, Exploring the Human Connection appeared first on McAfee Blogs.

In collaboration with Bill Siegel and Alex Holdtman from Coveware.

 

At the beginning of 2019, McAfee ATR published an article describing how the hasty attribution of Ryuk ransomware to North Korea was missing the point. Since then, collective industry peers discovered additional technical details on Ryuk’s inner workings, the overlap between Ryuk and Hermes2.1, and a detailed description of how the ransomware is piggybacking the infamous and ever evolving Trickbot as a primary attack vector. In this blog post we have teamed up with Coveware to take a closer look at the adversary and victim dynamics of Ryuk Ransomware. We structured our research using the Diamond threat model and challenged our existing hypotheses with fresh insights.

Introduction to The Diamond Model

Within Cyber Threat intelligence research, a popular approach is to model the characteristics of an attack using The Diamond Model of Intrusion Analysis. This model relates four basic elements of an intrusion: adversary, capabilities, infrastructure and victim.

For the Ryuk case described above the model can be applied as follows: “An Adversary, cyber-criminal(s), have a capability (Ryuk Ransomware) that is being spread via a TrickBot infection Infrastructure targeting specific victims.

Diamond model of Intrusion Analysis

The Diamond Model offers a holistic view of an intrusion that is a helpful guideline to shape the direction of intelligence research. By searching for relationships between two elements one can gather new evidence. For instance, by analyzing and reverse engineering a piece of malware one might uncover that a certain server is being used for command and control infrastructure, thus linking capability with infrastructure (as shown below).

Linking Infrastructure and Capability

Alternatively, one might search underground forums to find information on adversaries who sell certain pieces of malware, thus linking an adversary with a capability. For instance, finding the underground forum advertisement of Hermes2.1.

Linking Adversary and Capability

Analysis of Competing Hypotheses

In our earlier publication we explained The Analysis of Competing Hypotheses (ACH), the process of challenging formed hypotheses with research findings.
By following this method, we concluded that the strongest hypothesis is not the one with the most verifying evidence, but the one with the least falsifying evidence.

In order to construct a hypothesis with the least falsifying evidence we welcome research published by our industry peers to dissimilate insights that challenge our hypotheses. When we combined all the evidence with links on the diamond model, we discovered that one essential link wasn’t made, the link between adversary and victim.

Seeking New Insights Between Adversary and Victim

Despite published research, the direct link between adversary and victim remained relatively unexplored. Unlike most cybercrime, ransomware and digital extortion frequently creates a strong social connection between adversary and victim. The adversary has certain needs and views the victim as the means to fulfill those needs. The connection between an adversary and victim often generates valuable insights, especially in cases where (extensive) negotiation take place.

Luckily, one of our NoMoreRansom partners, Coveware, is specialized in ransomware negotiations and has gained valuable insights help us link adversary and victim.

The social connection between Adversary and Victim

Ransom Amounts and Negotiations

By aggregating ransomware negotiation and payment data, Coveware is able to identify strain-specific ransomware trends. With regards to Ryuk, it should be noted that ransom amounts average more than 10x the average, making it the costliest type of ransomware. Coveware also observed that some Ryuk ransoms were highly negotiable, while others were not. The bar-belled negotiation results generated an average ransom payment of $71k, a 60% discount from an average opening ask of $145k.

The bar-belled negotiation outcomes meant that some victims were stonewalled. These victims either lost their data or took on staggering financial risk to pay the ransom. The outcomes also imply that in certain cases the adversary would rather receive infrequent large windfalls (often in excess of 100BTC), while in other cases the adversary was keen to monetize every attack and accept lower amounts to ensure payment. This difference in modus operandi suggests that more than one cyber-criminal group is operating Ryuk ransomware.

Ransom Note and Negotiation Similarities and Differences

Similarities between Bitpaymer and Ryuk ransom notes have been observed before. While it is not uncommon for ransom notes to share similar language, sequences of phrases tend to remain within the same ransomware family. Slight copy+paste modifications are made to the ransom text as a variant is passed along to different groups, but large alterations are rarely made. Below is a comparison of a Bitpaymer initial email (left) and a standard Ryuk initial email (right).

A comparison of a Bitpaymer initial email (left) and a standard Ryuk initial email (right)

The shared language implies that text once unique to a Bitpaymer campaign was borrowed for a Ryuk campaign, possibly by an operator running simultaneous ransom campaigns of both Bitpaymer and Ryuk or the imitation can be considered as the sincerest form of flattery.

Different Initial Email Response May Be Different Adversaries?

A more dramatic scripted communication difference has been observed in the initial email response from Ryuk adversaries. The initial email response is typically identical within ransomware families belonging to the same campaign. When significant differences in length, language, and initial ransom amount appear in the initial email response we are comfortable assuming they belong to unique groups with unique modus operandi. This would mean that Ryuk in being spread by more than one actor group.

Below are two such Ryuk examples:

 

Post Payment Bitcoin Activity

A final indicator that multiple groups are running simultaneous Ryuk campaigns can be observed in the activity of bitcoin after it hits a ransom address. Surprisingly, despite the differences between negotiation outcome and initial communications, Coveware observed little difference between the BTC wallets (blacked out to protect victims) associated with the above cases. Initial comparison showed no meaningful discrepancy in difference between the time of a ransom payment and the time of a corresponding withdraw. Additionally, the distribution of funds upon withdrawal was consistently split between two addresses. Coveware will continue to monitor the funds associated with campaigns for meaningful indicators.

Ryuk Negotiating Profiles

With few exceptions, the rest of the email replies during a Ryuk extortion negotiation are extremely short and blunt. Typical replies and retorts are generally less than 10 written words and often just a single number if the ransom amount is the point of discussion. This correspondence is unique to Ryuk.

One reply did contain quite a remarkable expression; “à la guerre comme à la guerre,” to contextualize the methods and reasons for the cyber criminals’ attacks on western companies. The French expression originates from the seventeenth century and literally translates to “in war as in war” and loosely translates to: “In Harsh times one has to do with what’s available”. The striking thing about this expression is that is prominently featured in volume 30 of the collected works of the Soviet Revolutionary leader Vladimir Lenin. Lenin uses the expression to describe the struggle of his people during the war against western capitalism.

This concept of “The capitalistic West versus the Poor east” is actually something McAfee ATR sees quite often expressed by cyber criminals from some of the Post-Soviet republics. This expression may be a clear indicator of the origin and cultural view of the criminals behind Ryuk.

Ryuk poses existential risk to certain industries

Even though the average ransom discounts of Ryuk are large (~60%), the absolute level of the ransom is extreme. Accordingly, we have seen evidence that links ransom demands to the size of the network footprint of the victim company. However, this doesn’t mean that the ransom demand correlates to the victims actual operational and financial size.

Companies in the IT Hosting and the Freight and Logistics industries have been particularly susceptible to this discrepancy. Coveware has assisted at least 3 companies that have had to unwind their business when an affordable ransom amount, could not be reached. Typically, downtime costs are 10x the ransom amount, but in these industries downtime costs can be particularly extreme.

IT Hosting companies are of note as the size and number of their servers can make them appear like a large organization. Unfortunately, the business of hosting involves high fixed costs, low operating margins, and zero tolerance of downtime by end clients.  Hosting companies that get attacked typically have a few hours to restore service before their clients drop them for alternatives. Moreover, these companies suffer irreparable harm to their reputations, and may trigger SLA breaches that leave them exposed to liability.  The inability to pay a six-figure ransom has caused multiple hosting companies to shut down.

Freight and Logistics firms are also acutely exposed. These firms also present like larger firms given the volume of data they move and their network footprint. Additionally, attacks against Freight and Logistics firms can cause immediate supply chain issues for the victims’ end clients, who are subsequently forced to route through other service providers. Similar to IT Hosting, Freight and Logistics firms have low operating margins and end clients with little tolerance for service interruptions. The inability to pay or negotiate a large ransom has materially impacted several firms in this industry.

Ryuk Decryptor findings and issues

When victims do pay the exorbitant ransom amount, the criminals will provide a decryptor to unlock a their files. This decryptor is actually framework that needs to be loaded with a victim’s private RSA key, provided by the criminals, in order to decrypt. Ensuring that the provided decryptor will only work for this specific victim. This setup allows the criminals to quickly load a victim’s key in the framework and offer a custom decryptor with minimal code change while the underlaying framework remains the same.

From Coveware’s experience we have learned that the decryption process is quite cumbersome and full of possible fatal errors. Luckily Coveware was able to share the Ryuk decryptor with McAfee ATR in order to take a closer look at the issues and level of sophistication of the decryptor.

Once launched the first thing the decryptor does is to search the HKEY_CURRENT_USER Hive for a value pair named “svchos” in the path “SOFTWARE\Microsoft\Windows\CurrentVersion\Run” and delete the specific entry. This removes the persistence of the malware. Afterwards it will reboot the system and remove any remaining Ryuk malware still receding on the system.

Deleting the “svchos” value from the registry.

Once rebooted the user needs to run the tool again and the decryptor will provide two options to decrypt.

  • Decryption per file
  • Automatic decryption

The main interface of the Ryuk decryptor with the different menu options.

HERMES File maker

During the decryption process we have found that the decryptor searches for the known file marker string HERMES which is located in the encrypted file.

The HERMES marker clearly visible within the file

The fact that Ryuk ransomware adds HERMES filemarker string was already known, but discovering this specific check routine in the decryptor strengthens the hypotheses that Ryuk is a slightly modified version of Hermes2.1 ransomware kit that is sold online even more.

Decryptor Issues

While examining the decryptor we were astonished by the lack of sophistication and the amount of errors that resided within the code. Some of the most prominent issues were:

  • If there is a space in the Windows file path the decryptor will fail the decryption process.
  • If there is a quotation mark (“) in the file path the decryptor will report an error that it cannot find the specific file.
  • The decryptor uses the “GetVersionExW” function to determine the windows version, from Windows 8.1. the value returned by this API has changed and the decryptor isn’t designed to handle this value.
  • The decryptor doesn’t remove the .RYUK extension and replace it with the original extension. So, there is no way the name of the file can give an indication towards the type of the file, something that can be extremely labor intensive for enterprise victims.
  • When choosing the manual option in the decryptor, the user has to supply a path of the specific file or choose “0” to finish. However, choosing a “0” will put the decryptor into an infinite loop.

Looking at the decryptor, it is very worrisome to see that the criminals behind Ryuk can get away with such bad programming. It shows a clear lack of empathy towards their victims and the absence of solid coding skills. Victims who do pay the exorbitant ransom demand are far from in the clear. The decryptor offered by the criminals has a very high risk of malfunctioning, resulting in permanent damage to their precious files. Victims should always make an exact copy of the encrypted hard disk before trying to use the decryptor.

Call to action in piecing the different parts together

By combining all the fresh insights with the information that was already discovered by ourselves and industry peers we can start defining our leading hypotheses around Ryuk. Based on this hypothesis, we will actively look for falsifying evidence. We encourage the security community to participate in this process. We realize that only by collaboration can we piece the different parts of the Ryuk puzzle together.

By now it should be without question that involvement of the DPRK is the least likely hypothesis. Our leading Hypothesis on Ryuk until proven otherwise is;

Ryuk is a direct descendant from Hermes2.1 with slight modifications, based on the code overlap in the ransomware as well as the decryptor. Ryuk is not designed to be used in a largescale corporate environment, based on all the scalability issues in the decryptor. At this moment there are several actors or actor-groups spreading Ryuk, based on the extortion modus operandi and different communications with the victims. The actors or actor-groups behind Ryuk have a relationship with one of the Post-Soviet republics, based on the Russian found in one of the encrypted files and the cultural references observed in the negotiations. The actors behind Ryuk most likely have an affiliation or relationship with the actors behind Trickbot and, based on their TTP, are better skilled at exploitation and lateral movement than pure Ransomware development.

Conclusion

In the last seven months Ryuk has proven to be a highly profitable form of ransomware, despite the poor programming behind it and its decryptor. The criminals have proven to be ruthless and several of their victims were forced to wind down their businesses after they were unable to afford the exorbitant ransom.

When a company does give in to the high demands it is extra painful to see a situation occur where they are permanently unable to recover their files due to the faulty decryptor.

A solid data loss prevention strategy still remains the best advice against all forms of ransomware, for general prevention advice please visit NoMoreRansom. Always seek professional assistance when you are faced with a targeted ransomware attack such as Ryuk.

The post Ryuk, Exploring the Human Connection appeared first on McAfee Blogs.

Ryuk Ransomware Attack: Rush to Attribution Misses the Point

Senior analyst Ryan Sherstobitoff contributed to this report. During the past week, an outbreak of Ryuk ransomware that impeded newspaper printing services in the United States has garnered a lot of attention. To determine who was behind the attack many have cited past research that compares code from Ryuk with the older ransomware Hermes to […]

The post Ryuk Ransomware Attack: Rush to Attribution Misses the Point appeared first on McAfee Blogs.

Senior analyst Ryan Sherstobitoff contributed to this report.

During the past week, an outbreak of Ryuk ransomware that impeded newspaper printing services in the United States has garnered a lot of attention. To determine who was behind the attack many have cited past research that compares code from Ryuk with the older ransomware Hermes to link the attack to North Korea. Determining attribution was largely based on the fact that the Hermes ransomware has been used in the past by North Korean actors, and code blocks in Ryuk are similar to those in Hermes.

The McAfee Advanced Threat Research team has investigated this incident and determined how the malware works, how the attackers operate, and how to detect it. Based on the technical indicators, known cybercriminal characteristics, and evidence discovered on the dark web, our hypothesis is that the Ryuk attacks may not necessarily be backed by a nation-state, but rather share the hallmarks of a cybercrime operation.

How McAfee approaches attribution

Attribution is a critical part of any cybercrime investigation. However, technical evidence is often not enough to positively identify who is behind an attack because it does not provide all the pieces of the puzzle. Artifacts do not all appear at once; a new piece of evidence unearthed years after an attack can shine a different light on an investigation and introduce new challenges to current assumptions.

Ryuk attack: putting the pieces together

In October 2017, we investigated an attack on a Taiwanese bank. We discovered the actors used a clever tactic to distract the IT staff: a ransomware outbreak timed for the same moment that the thieves were stealing money. We used the term pseudo-ransomware to describe this attack. The malware was Hermes version 2.1.

One of the functions we often see in ransomware samples is that they will not execute if the victim’s system language is one of the following:

  • 419 (Russian)
  • 422 (Ukrainian)
  • 423 (Belarusian)

That was October 2017. Searching earlier events, we noticed a posting from August 2017 in an underground forum in which a Russian-speaking actor offered the malware kit Hermes 2.1 ransomware:

What if the actor who attacked the Taiwanese bank simply bought a copy of Hermes and added it to the campaign to cause the distraction? Why go to the trouble to build something, when the actor can just buy the perfect distraction in an underground forum?

In the same underground forum thread we found a post from October 22, 2018, mentioning Ryuk.

This post contains a link to an article in the Russian security magazine Xakep.ru (“Hacker”) discussing the emergence of Ryuk and how it was first discovered by MalwareHunterTeam in August 2018. This first appearance came well before last week’s attack on newspaper printing services.

Manga connection

Ryuk, according to Wikipedia, refers to a Japanese manga character from the series “Death Note.” Ryuk apparently drops a death note, a fitting name for ransomware that drops ransom notes.

Ransomware is typically named by its cybercriminal developer, as opposed to the naming of state-sponsored malware, which is mostly is done by the security industry. It seems the criminals behind Ryuk are into manga.

The use of manga character names and references is common in the cybercriminal scene. We often come across manga-inspired nicknames and avatars in underground forums.

Technical indicators

Looking at research from our industry peers comparing Ryuk and Hermes, we notice that the functionalities are generally equal. We agree that the actors behind Ryuk have access to the Hermes source code.

Let’s dive a bit deeper into Ryuk and compare samples over the last couple of months regarding compilation times and the presence of program database (PDB) paths:

We can see the PDB paths are almost identical. When we compare samples from August and December 2018 and focus on the checksum values of the executables’ rich headers, they are also identical.

From a call-flow perspective, we notice the similarities and evolution of the code:

The Hermes 2.1 ransomware kit, renamed and redistributed as Ryuk.

The author and seller of Hermes 2.1 emphasizes that he is selling is a kit and not a service. This suggests that a buyer of the kit must do some fine tuning by setting up a distribution method (spam, exploit kit, or RDP, for example) and infrastructure to make Hermes work effectively. If changing a name and ransom note are part of these tuning options, then it is likely that Ryuk is an altered version Hermes 2.1.

Attribution: analyzing competing hypotheses

In the race to determine who is behind an attack, research facts (the What and How questions) are often put aside to focus on attribution (the Who question). Who did it? This pursuit is understandable yet fundamentally flawed. Attribution is crucial, but there will always be unanswered questions. Our approach focuses on answering the What and How questions by analyzing the malware, the infrastructure involved, and the incident response performed at the victim’s site.

Our approach is always to analyze competing hypotheses. When investigating an incident, we form several views and compare all the artifacts to support these hypotheses. We try not only to seek verifying evidence but also actively try to find evidence that falsifies a hypothesis. Keeping our eyes open for falsifying facts and constantly questioning our results are essential steps to avoid conformation bias. By following this method, we find the strongest hypothesis is not the one with the most verifying evidence, but the one with the least falsifying evidence.

Examining competing hypotheses is a scientific approach to investigating cyber incidents. It may not help with the race to attribution, but it ensures the output is based on available evidence.

The most likely hypothesis in the Ryuk case is that of a cybercrime operation developed from a tool kit offered by a Russian-speaking actor. From the evidence, we see sample similarities over the past several months that indicate a tool kit is being used. The actors have targeted several sectors and have asked a high ransom, 500 Bitcoin. Who is responsible? We do not know. But we do know how the malware works, how the attackers operate, and how to detect the threat. That analysis is essential because it allows us to serve our customers.

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Fallout Exploit Kit Releases the Kraken Ransomware on Its Victims

Alexandr Solad and Daniel Hatheway of Recorded Future are coauthors of this post. Rising from the deep, Kraken Cryptor ransomware has had a notable development path in recent months. The first signs of Kraken came in mid-August on a popular underground forum. In mid-September it was reported that the malware developer had placed the ransomware, …

The post Fallout Exploit Kit Releases the Kraken Ransomware on Its Victims appeared first on McAfee Blogs.

Alexandr Solad and Daniel Hatheway of Recorded Future are coauthors of this post.

Rising from the deep, Kraken Cryptor ransomware has had a notable development path in recent months. The first signs of Kraken came in mid-August on a popular underground forum. In mid-September it was reported that the malware developer had placed the ransomware, masquerading as a security solution, on the website SuperAntiSpyware, infecting systems that tried to download a legitimate version of the antispyware software.

Kraken’s presence became more apparent at the end of September, when the security researcher nao_sec discovered that the Fallout Exploit Kit, known for delivering GandCrab ransomware, also started to deliver Kraken.

The McAfee Advanced Threat Research team, working with the Insikt group from Recorded Future, found evidence of the Kraken authors asking the Fallout team to be added to the Exploit Kit. With this partnership, Kraken now has an additional malware delivery method for its criminal customers.

We also found that the user associated with Kraken ransomware, ThisWasKraken, has a paid account. Paid accounts are not uncommon on underground forums, but usually malware developers who offer services such as ransomware are highly trusted members and are vetted by other high-level forum members. Members with paid accounts are generally distrusted by the community.

 

Kraken Cryptor’s developers asking to join the Fallout Exploit Kit.

Kraken Cryptor announcement.

The ransomware was announced, in Russian, with the following features:

  • Encoded in C# (.NET 3.5)
  • Small stub size ~85KB
  • Fully autonomous
  • Collects system information as an encrypted message for reference
  • File size limit for encryption
  • Encryption speed faster than ever
  • Uses a hybrid combination of encryption algorithms (AES, RC4, Salsa20) for secure and fast encryption with a unique key for each file
  • Enables the use of a network resource and adds an expansion bypass mode for encrypting all files on non-OS disks
  • Is impossible to recover data using a recovery center or tools without payment
  • Added antidebug, antiforensic methods

Kraken works with an affiliate program, as do ransomware families such as GandCrab. This business scheme is often referred to a Ransomware-as-a-Service (RaaS).

Affiliates are given a new build of Kraken every 15 days to keep the payload fully undetectable from antimalware products. According to ThisWasKraken, when a victim asks for a free decryption test, the affiliate member should send one of the victim’s files with its associated unique key to the Kraken Cryptor ransomware support service. The service will decrypt the file and resend it to the affiliate member to forward the victim. After the victim pays the full ransom, the affiliate member sends a percentage of the received payment to the RaaS developers to get a decryptor key, which is forwarded to the victim. This system ensures the affiliate pays a percentage to the affiliate program and does not simply pocket the full amount. The cut for the developers offers them a relatively safe way of making a profit without exposing themselves to the risk of spreading ransomware.

We have observed that the profit percentage for the developers has decreased from 25% in Version 1 to 20% in Version 2. The developers might have done this to attract more affiliates. To enter the program, potential affiliates must complete a form and pay $50 to be accepted.

In the Kraken forum post it states that the ransomware cannot be used in the following countries:

  • Armenia
  • Azerbaijan
  • Belarus
  • Estonia
  • Georgia
  • Iran
  • Kazakhstan
  • Kyrgyzstan
  • Latvia
  • Lithuania
  • Moldova
  • Russia
  • Tajikistan
  • Turkmenistan
  • Ukraine
  • Uzbekistan

On October 21, Kraken’s authors released Version 2 of the affiliate program, reflecting the ransomware’s popularity and a fresh release. At the same time, the authors published a map showing the distribution of their victims:

Note that some of the countries on the developers’ exclusion list have infections.

Video promotions

The first public release of Kraken Cryptor was Version 1.2; the latest is Version 2.07. To promote the ransomware, the authors created a video showing its capabilities to potential customers. We analyzed the metadata of the video and believe the authors created it along with the first version, released in August.

In the video, the authors show how fast Kraken can encrypt data on the system:

Kraken ransomware in action.

Actor indications

The Advanced Threat Research team and Recorded Future’s Insikt group analyzed all the forum messages posted by ThisWasKraken. Based on the Russian language used in the posts, we believe ThisWasKraken is neither a native Russian nor English speaker. To make forum posts in Russian, the actor likely uses an automated translation service, suggested by the awkward phrasing indicative of such a service. In contrast, the actor is noticeably more proficient in English, though they make mistakes consistently in both sentence structure and spelling. English spelling errors are also noticeable in the ransom note.

ThisWasKraken is likely part of a team that is not directly involved in the development of the ransomware. The actor’s role is customer facing, through the Jabber account [email protected][.]im. Communications with ThisWasKraken show that the actor refers all technical issues to the product support team at [email protected][.]com.

Payments

Bitcoin is the only currency the affiliate program uses. Insikt Group identified several wallets associated with the operation. Kraken’s developers appear to have choose BitcoinPenguin, an online gambling site as the primary money laundering conduit. It is very uncommon for criminal actors, and specifically ransomware operators, to bypass traditional cryptocurrency exchangers when laundering stolen funds. One of the decisive factors for the unusual choice was likely BitcoinPenguin’s lack of requiring identity verification by its members, allowing anyone to maintain an anonymous cryptocurrency wallet.

Although in response to regulatory demands cryptocurrency exchangers continue to stiffen their registration rules, online crypto casinos do not have to follow the same know-your-customer guidelines, providing a convenient loophole for all kinds of money launderers.

Bitcoin transactions associated with Kraken analyzed with the Crystal blockchain tool. The parent Bitcoin wallet is 3MsZjBte81dvSukeNHjmEGxKSv6YWZpphH.

Kraken Cryptor at work

The ransomware encrypts data on the disk very quickly and uses external tools, such as SDelete from the Sysinternals suite, to wipe files and make file recovery harder.

The Kraken Cryptor infection scheme.

The ransomware has implemented a user account control (UAC) bypass using the Windows Event Viewer. This bypass technique is used by other malware families and is quite effective for executing malware.

The technique is well explained in an article by blogger enigma0x3.

We analyzed an early subset of Kraken ransomware samples and determined they were still in the testing phase, adding and removing options. The ransomware has implemented a “protection” to delete itself during the infection phase:

“C:\Windows\System32\cmd.exe” /C ping 127.0.0.1 -n 3 > NUL&&del /Q /F /S “C:\Users\Administrator\AppData\Local\Temp\krakentemp0000.exe”

This step is to prevent researchers and endpoint protections from catching the file on an infected machine.

Kraken encrypts user files with a random name and drops the ransom note demanding the victim to pay to recover them. McAfee recommends not paying ransoms because doing so contributes to the development of more ransomware families.

Kraken’s ransom note.

Each file extension is different; this technique is often used by specific ransomware families to bypass endpoint protection systems.

Kraken delivered by the exploit kit bypasses the UAC using Event Viewer, drops a file on the system, and executes it through the UAC bypass method.

The binary delivered by the exploit kit.

The authors of the binary forgot during the compilation of the first versions to delete the PDB reference, revealing that the file has a relationship with Kraken Cryptor:

The early versions contained the following path:

C:\Users\Krypton\source\repos\UAC\UAC\obj\\Release\UAC.pdb.

Later versions dropped the PDB path together with the Kraken loader.

Using SysInternals tools

One unique feature of this ransomware family is the use of SDelete. Kraken uses a .bat file to perform certain operations, making file recovery much more challenging:

Kraken downloads SDelete from the Sysinternals website, adds the registry key accepting the EULA to avoid the pop-up, and executes it with the following arguments:

sdelete.exe -c -z C

The SDelete batch file makes file recovery much harder by overwriting all free space on the drive with zeros, deleting the Volume Shadow Copies, disabling the recovery reboot option and finally rebooting the system after 300 seconds.

Netguid comparison

The earlier versions of Kraken were delivered by a loader before it moved to a direct execution method. The loader we examined contained a specific netguid. With this, we found additional samples of the Kraken loader on VirusTotal:

Not only the loader had a specific netguid but the compiled versions of Kraken also shared a netguid, making it possible to continue hunting samples:

Comparing versions

Kraken uses a configuration file in every version to set the variables for the ransomware. This file is easily extracted for additional analysis.

Based on the config file we have discovered nine versions of Kraken:

  • 2
  • 3
  • 5
  • 5.2
  • 5.3
  • 6
  • 0
  • 0.4
  • 0.7

By extracting the config files from all the versions, we built the following overview of features. (The √ means the feature is present.)

All the versions we examined mostly contain the same options, changing only in some of them the antivirtual protection and antiforensic capabilities. The latest version, Kraken 2.0.7, changed its configuration scheme. We will cover that later in this article.

Other differences in Kraken’s config file include the list of countries excluded from encryption. The standouts are Brazil and Syria, which were not named in the original forum advertisement.

Having an exclusion list is a common method of cybercriminals to avoid prosecution. Brazil’s addition to the list in Version 1.5 suggests the involvement of a Brazilian affiliate. The following table shows the exclusion list by country and version. (The √ means the country appears on the list.)

All the Kraken releases have excluded the same countries, except for Brazil, Iran, and Syria.

Regarding Syria: We believe that the Kraken actors have had the same change of heart as the actors behind GandCrab, who recently released decryption keys for Syrian victims after a tweet claimed they had no money to pay the ransoms.

 

GandCrab’s change of heart regarding Syrian victims.

Version 2.0.7

The most recent version we examined comes with a different configuration scheme:

This release has more options. We expect this malware will be more configurable than other active versions.

APIs and statistics

One of the new features is a public API to track the number of victims:

Public API to track the number of victims. Source: Bleeping Computer.

Another API is a hidden service to track certain statistics:

 

The Onion URL can be found easily in the binary:

The endpoint and browser Kraken uses is hardcoded in the config file:

Kraken gathers the following information from every infection:

  • Status
  • Operating system
  • Username
  • Hardware ID
  • IP address
  • Country
  • City
  • Language
  • HDCount
  • HDType
  • HDName
  • HDFull
  • HDFree
  • Privilege
  • Operate
  • Beta

Kraken infrastructure

In Versions 1.2 through 2.04 Kraken contacts blasze[.]tk to download additional files. The site has Cloudflare protection to mitigate against DDoS attacks:

The domain is not accessible from many countries:

 

McAfee coverage

McAfee detects this threat with the following signatures:

  • Artemis!09D3BD874D9A
  • Artemis!475A697872CA
  • Artemis!71F510C40FE5
  • Artemis!99829D5483EF
  • Artemis!CE7606CFDFC0
  • Artemis!F1EE32E471A4
  • RDN/Generic.dx
  • RDN/Generic.tfr
  • RDN/Ransom

Indicators of compromise

Kraken loader hashes

  • 564154a2e3647318ca40a5ffa68d06b1bd40b606cae1d15985e3d15097b512cd
  • 53a28d3d29e655deca6702c98e71a9bd52a5a6de05524234ab362d27bd71a543

Kraken ransomware samples hashes

  • 047de76c965b9cf4a8671185d889438e4b6150326802e87470d20a3390aad304
  • 0b6cd05bee398bac0000e9d7032713ae2de6b85fe1455d6847578e9c5462391f
  • 159b392ec2c052a26d6718848338011a3733c870f4bf324863901ec9fbbbd635
  • 180406f298e45f66e205bdfb2fa3d8f6ead046feb57714698bdc665548bebc95
  • 1d7251ca0b60231a7dbdbb52c28709a6533dcfc4a339f4512955897c7bb1b009
  • 2467d42a4bdf74147ea14d99ef51774fec993eaef3c11694125a3ced09e85256
  • 2b2607c435b76bca395e4ef4e2a1cae13fe0f56cabfc54ee3327a402c4ee6d6f
  • 2f5dec0a8e1da5f23b818d48efb0b9b7065023d67c617a78cd8b14808a79c0dc
  • 469f89209d7d8cc0188654e3734fba13766b6d9723028b4d9a8523100642a28a
  • 4f13652f5ec4455614f222d0c67a05bb01b814d134a42584c3f4aa77adbe03d0
  • 564154a2e3647318ca40a5ffa68d06b1bd40b606cae1d15985e3d15097b512cd
  • 61396539d9392ae08b2c9836dd19a58efb541cf0381ea6fef28637aae63084ed
  • 67db0f639d5f4c021efa9c2b1db3b3bc85b2db920859dbded5fed661cc81282d
  • 713afc925973a421ff9328ff02c80d38575fbadaf27a1db0063b3a83813e8484
  • 7260452e6bd05725074ba92b9dc8734aec12bbf4bbaacd43eea9c8bbe591be27
  • 7747587608db6c10464777bd26e1abf02b858ef0643ad9db8134e0f727c0cd66
  • 7e0ee0e707db426eaf25bd0924631db969bb03dd9b13addffbcc33311a3b9aa7
  • 7fb597d2c8ed8726b9a982b2a84d1c9cc2af65345588d42dd50c8cebeee03dff
  • 85c75ac7af9cac6e2d6253d7df7a0c0eec6bdd71120218caeaf684da65b786be
  • 8a0320f3fee187040b1922c6e8bdf5d6bacf94e01b90d65e0c93f01e2abd1e0e
  • 97ed99508e2fae0866ad0d5c86932b4df2486da59fc2568fb9a7a4ac0ecf414d
  • 9c88c66f44eba049dcf45204315aaf8ba1e660822f9e97aec51b1c305f5fdf14
  • a33dab6d7adb83691bd14c88d7ef47fa0e5417fec691c874e5dd3918f7629215
  • b639e26a0f0354515870ee167ae46fdd9698c2f0d405ad8838e2e024eb282e39
  • cae152c9d91c26c1b052c82642670dfb343ce00004fe0ca5d9ebb4560c64703b
  • d316611df4b9b68d71a04ca517dbd94615a77a87f7a8c270d100ef9729a4e122
  • e39d5f664217bda0d95d126cff58ba707d623a58a750b53c580d447581f15af6
  • f7179fcff00c0ec909b615c34e5a5c145fedf8d9a09ed04376988699be9cc6d5
  • f95e74edc7ca3f09b582a7734ad7a547faeb0ccc9a3370ec58b9a27a1a6fd4a7
  • fea3023f06d0903a05096f1c9fc7113bea50b9923a3c024a14120337531180cd
  • ff556442e2cc274a4a84ab968006350baf9897fffd680312c02825cc53b9f455

Authentihash

  • 83b7ed1a0468394fc9661d07b9ad1b787f5e5a85512ae613f2a04a7442f21587
  • b821eb60f212f58b4525807235f711f11e2ef285630604534c103df74e3da81a
  • 0c4e0359c47a38e55d427894cc0657f2f73136cde9763bbafae37c916cebdd2a

Imphash

  • f34d5f2d4577ed6d9ceec516c1f5a744

Jabber

Email addresses found in the binaries and configuration files

Bitcoin address

  • 3MsZjBte81dvSukeNHjmEGxKSv6YWZpphH

PDBs found in the loader samples

  • C:\Users\Krypton\source\repos\UAC\UAC\obj\\Release\UAC.pdb

Associated Filenames

  • C:\ProgramData\Safe.exe C:\ProgramData\EventLog.txt # How to Decrypt Files.html
  • exe
  • exe
  • bat
  • <random>.bat
  • exe
  • exe
  • <random>.exe
  • exe
  • exe
  • exe
  • exe
  • exe
  • exe
  • exe
  • exe
  • exe
  • _exe
  • exe

Ransomware demo version

  • https://www76.zippyshare.com/v/5fMpcbdo/file[.]html

Kraken Unique Key

MITRE ATT&CK™ techniques

  • Data compressed
  • Email collection
  • File and directory
  • File deletion
  • Hooking
  • Kernel modules and extensions
  • Modify registry
  • Process injection
  • Query registry
  • Remote system
  • Security software
  • Service execution
  • System information
  • System time

Yara rules

 

The post Fallout Exploit Kit Releases the Kraken Ransomware on Its Victims appeared first on McAfee Blogs.

Rapidly Evolving Ransomware GandCrab Version 5 Partners With Crypter Service for Obfuscation

The GandCrab ransomware, which first appeared in January, has been updated rapidly during its short life, with Version 5.0.2 appearing this month. In this post we will examine the latest version and how the authors have improved the code (and in some cases have made mistakes). McAfee gateway and endpoint products are able to protect …

The post Rapidly Evolving Ransomware GandCrab Version 5 Partners With Crypter Service for Obfuscation appeared first on McAfee Blogs.

The GandCrab ransomware, which first appeared in January, has been updated rapidly during its short life, with Version 5.0.2 appearing this month. In this post we will examine the latest version and how the authors have improved the code (and in some cases have made mistakes). McAfee gateway and endpoint products are able to protect customers from known variants of this threat.

The GandCrab authors have moved quickly to improve the code and have added comments to provoke the security community, law enforcement agencies, and the NoMoreRansom organization. Despite the agile approach of the developers, the coding is not professional and bugs usually remain in the malware (even in Version 5.0.2), but the speed of change is impressive and increases the difficulty of combating it.

The group behind GandCrab has achieved cult status in underground forums; the authors are undoubtedly confident and have strong marketing skills, but flawless programming is not one of their strengths.

Underground alliances

On September 27, the GandCrab crew announced Version 5 with the same showmanship as its earlier versions. GandCrab ransomware has gained a lot of attention from security researchers as well as the underground. The developers market the affiliate program like a “members-only club” and new affiliates are lining up to join, in the hope of making easy money through the large-scale ransomware extortion scheme.

The prospect of making money not only attracts new affiliates, but also leads to the formation of new alliances between GandCrab and other criminal services that strengthen the malware’s supply and distribution networks. One of these alliances became obvious during Version 4, in which the ransomware started being distributed through the new Fallout exploit kit. This alliance was again emphasized in the GandCrab Version 5 announcement, as the GandCrab crew openly endorsed FalloutEK.

The GandCrab Version 5 announcement.

With Version 5, yet another alliance with a criminal service has been formed. The malware crypter service NTCrypt announced that it is partnering with the GandCrab crew. A crypter service provides malware obfuscation to evade antimalware security products.

The NTCrypt-GandCrab partnership announcement offering a special price for GandCrab users.

The partnership between GandCrab and NTCrypt was established in a novel way. At the end of September, the GandCrab crew started a “crypt competition” on a popular underground forum to find a new crypter service they could partner with. NTCrypt applied and eventually won the competition.

The “crypt competition” announcement.

This novel approach emphasizes once more the cult status GandCrab has in the underground community. For a criminal business such as GandCrab, building these alliances makes perfect sense: They increase the ease of operation and a trusted affiliate network minimizes their risk exposure by allowing them to avoid less-trusted suppliers and distributors.

For the security community it is worrisome to see that GandCrab’s aggressive marketing strategy seems to be paying off. It is generating a strong influx of criminal interest and allows the GandCrab crew to form alliances with other essential services in the cybercriminal supply chain.

GandCrab overview

GandCrab Version 5 uses several mechanisms to infect systems. The following diagram shows an overview of GandCrab’s behavior.

GandCrab Version 5 Infection

Entry vector

GandCrab uses several entry vectors:

  • Remote desktop connections with weak security or bought in underground forums
  • Phishing emails with links or attachments
  • Trojanized legitimate programs containing the malware, or downloading and launching it
  • Exploits kits such as RigEK and others such as FalloutEK
  • PowerShell scripts or within the memory of the PowerShell process (the later mainly in Version 5.0.2)
  • Botnets such as Phorpiex (an old botnet that spread not only this malware but many others)

The goal of GandCrab, as with other ransomware, is to encrypt all or many files on an infected system and insist on payment to unlock them. The developer requires payment in cryptocurrency, primarily Dash (or Bitcoin in some older versions), because it is complex to track and quick to receive the payment.

The malware is usually, but not always, packed. We have seen variants in .exe format (the primary form) along with DLLs. GandCrab is effectively ransomware as a service; its operators can choose which version they want.

Version 5.0

This version has two releases. The first works only on Windows 7 or later due to a big mistake in the compiling time. Version 5.0 carries two exploits that try to elevate privileges. It checks the version of the operating system and the TokenIntegrityLevel class of the process. If the SID Subauthority is SECURITY_MANDATORY_LOW_RID (0x1000), it tries to execute the exploits if it also passed one previous check of a mutex value.

One release is the exploit released in August on Twitter and GitHub by the hacker “SandboxEscaper.” The original can be found at this link. The Twitter handle for this hacker is https://twitter.com/sandboxescaper.

This exploit tries to use a problem with the Task System in Windows when the operating system improperly handles calls to an advanced local procedure call.

The GandCrab authors claim there is no CVE of this exploit, but that is incorrect. It falls under CVE-2018-8440. This exploit can affect versions Windows 7 through Windows 10 Server. More information about this exploit can be found at this link.

In the first release of Version 5.0, the malware authors wrote the code exploit using normal calls to the functions. Thus at compiling time the binary has the IAT filled with the DLL needed for some calls. This DLL does not exist in Windows Vista and XP, so the malware fails to run in these systems, showing an error.

Import of xpsprint.dll that will not run on Windows XP or Vista.

The exploit using direct calls.

This release published an HTML file after encrypting the user’s files, but this file was faulty because it did not always have the information needed to decrypt the user’s files.

The second release uses dynamic calls and obfuscates the strings of the exploit, as shown in the previous image. (Earlier they were in plain text.)

The exploit with dynamic calls and obfuscated strings.

The second exploit is covered under CVE-2018-8120, which in Windows 7, Windows Server 2008 R2 and Windows Server 2008 allows an elevation of privileges from the kernel. Thanks to a faulty object in the token of the System process, changing this token in the malware results in executing the malware with System privileges.

Executing the exploit CVE-2018-8120.

You can read more about this exploit on mcafee.com.

The malware checks the version of the operating system and type of user and whether it can get the token elevation information of its own process before employing the use of exploits. In some cases, it fails to infect. For example, in Windows XP the second release of Version 5 runs but does not encrypt the files. (We thank fellow researcher Yassine Lemmou, who shared this information with us.)

We and Lemmou know where the problem is in Version 5.0.2. A few changes to the registry could make the malware run correctly, but we do not want to help the malware authors fix their product. Even though GandCrab’s authors quickly repair mistakes as they are pointed out, they still fail to find some of the basic errors by themselves. (McAfee has had no contact with GandCrab’s developers.)

The second release writes a random extension of five letters instead of using the normal .CRAB or .KRAB extension seen in previous versions. The malware keeps this information as binary data in a new registry entry in the subkey “ext_data\data” and in the value entry of “ext.”

A new registry entry to hold the random extension.

The malware tries creating this new entry in the root key of HKEY_LOCAL_MACHINE. If it cannot—for example, because the user does not have admin rights—it places the entry in the root key HKEY_CURRENT_USER. This entry is deleted in some samples after the files have been encrypted.

Version 5.0.1

This version fixed some internal bugs in the malware but made no other notable changes.

Version 5.0.2

This version changes the random extension length from 5 to 10 characters and fixes some internal bugs. Other bugs remain, however, meaning files cannot always be encrypted.

The latest

This section is based on the latest version of the malware (Version 5.0.2 on October 4), though some elements appear in earlier releases of Version 5. Starting with this version, the malware uses two exploits to try to elevate privileges in the system.

The first exploit uses a dynamic call to the function IsWoW64Process to detect whether the operating system is running in 32 or 64 bits.

The dynamic call to IsWoW64Process with obfuscated strings.

Depending on the result, the malware has two embedded DLLs, encrypted with a simple operation XOR 0x18.

Decrypting the DLL to load with the exploit and fix the header.

The malware authors use a clever trick with fuzzing to avoid detection: The first two bytes of the DLL are trash, something that is later fixed, as we see in the preceding image.

After decryption and loading the exploit, this DLL creates a mutex in the system and some pipes to communicate with the main malware. The malware creates a pipe that the DLL reads later and prepares strings as the mutex string for the DLL.

Preparing the string for the DLL.

The DLL has dummy strings for these strings.

Creating the new mutex and relaunching the process.

This mutex is checked when the malware starts. The function returns a 1 or 0, depending on whether it can open the mutex. Later, this result is checked and if the mutex can be opened the malware will avoid checking the version and will not use the two new exploits to elevate privileges.

Opening the new mutex to check if there is a need to run the exploits.

As with GandCrab Version 4.x and later, the malware later checks the version. If it is Vista or later, it tries to get the “TokenIntegrityLevel” class and relaunch the binary to elevate its privilege with a call to “ShellExecuteExW” with the “runas” application. If the system is Windows XP, the code will avoid that and continue in its normal flow.

This mutex is never created for the main malware; it is created for the DLL loaded using the exploit. To better understand this explanation, this IDA snippet may help:

Explaining the check of mutex and exploits.

This version changes the desktop wallpaper, which is created at runtime and is filled with the extension generated to encrypt the files. (The ransom note text or HTML has the name: <extension_in_uppercase>_DECRYPT. <txt|html>) and the user name of the machine.)

Creating the new wallpaper at runtime.

The username is checked with “SYSTEM.” If the user is “SYSTEM,” the malware puts the name “USER” in the wallpaper.

Checking the name of the user for the wallpaper.

The wallpaper is created in the %TEMP% folder with the name pidor.bmp.

Creating the wallpaper in the temp folder.

Here is an example of strings used in the wallpaper name and to check the name of the user and the format string, whether it is another user, or the final string in the case of SYSTEM user with USER in uppercase.

The name of the wallpaper and special strings.

Finally, the wallpaper is set for any user other than SYSTEM:

Changing the wallpaper.

The malware detects the language of the system and decrypts the strings and writes the correct ransom note in the language of the system.

Coverage

Customers of McAfee gateway and endpoint products are protected against the latest GandCrab versions. Detection names include Ran-Gandcrabv4! and many others.

An independent researcher, Twitter user Valthek, has also created several vaccines. (McAfee has verified that these vaccines are effective.) The version for GandCrab 4.x through 5.0.2 can prevent the files from being encrypted.

For Version 4.x, the deletion of shadow volumes cannot be avoided but at least the files themselves are kept safe.

For Version 5.x, encrypting the files can be avoided but not the creation and changing of the wallpaper, which the malware will still corrupt. The malware cannot create random extensions to encrypt the files but will prepare the string. Running the vaccine a second time removes the wallpaper if it is in the %TEMP% folder.

The vaccine has versions with and without persistence. The version with persistence creates a random filename in a special folder and writes a special random entry in the registry to run each time with the system. In this case, the machine will always be protected against this malware (at least in its current state of October 10, and perhaps in the future).

 

Indicators of compromise

These samples use the following MITRE ATT&CK™ techniques:

  • File deletion
  • System information discovery
  • Execution through API
  • Execution through WMIC
  • Application process discovery: to detect antimalware and security products as well as normal programs
  • Query registry: to get information about keys that the malware needs to create or read
  • Modify registry
  • File and directory discovery: to search for files to encrypt
  • Discovery of network shares to encrypt them
  • Encrypt files
  • Process discovery: enumerating all processes on the endpoint to kill some special ones
  • Create files
  • Elevation of privileges
  • Change wallpaper
  • Flood the network with connections
  • Create mutants

Hashes 

  • e168e9e0f4f631bafc47ddf23c9848d7: Version 5.0
  • 6884e3541834cc5310a3733f44b38910: Version 5.0 DLL
  • 2d351d67eab01124b7189c02cff7595f: Version 5.0.2
  • 41c673415dabbfa63905ff273bdc34e9: Version 5.0.2
  • 1e8226f7b587d6cd7017f789a96c4a65: DLL for 32-bit exploit
  • fb25dfd638b1b3ca042a9902902a5ff9: DLL for 64-bit exploit
  • df1a09dd1cc2f303a8b3d5097e53400b: botnet related to the malware (IP 92.63.197.48)

 

The post Rapidly Evolving Ransomware GandCrab Version 5 Partners With Crypter Service for Obfuscation appeared first on McAfee Blogs.