Category: Advanced Persistent Threats

Aug 09 2018

Examining Code Reuse Reveals Undiscovered Links Among North Korea’s Malware Families

This research is a joint effort by Jay Rosenberg, senior security researcher at Intezer, and Christiaan Beek, lead scientist and senior principal engineer at McAfee. Intezer has also posted this story. 

Attacks from the online groups Lazarus, Silent Chollima, Group 123, Hidden Cobra, DarkSeoul, Blockbuster, Operation Troy, and 10 Days of Rain are believed to have come from North Korea. But how can we know with certainty? And what connection does a DDoS and disk-wiping attack from July 4, 2009, have with WannaCry, one of the largest cyberattacks in the history of the cyber sphere?  

From the Mydoom variant Brambul to the more recent Fallchill, WannaCry, and the targeting of cryptocurrency exchanges, we see a distinct timeline of attacks beginning from the moment North Korea entered the world stage as a significant threat actor.

Bad actors have a tendency to unwittingly leave fingerprints on their attacks, allowing researchers to connect the dots between them. North Korean actors have left many of these clues in their wake and throughout the evolution of their malware arsenal.

This post reflects months of research; in it we will highlight our code analysis illustrating key similarities between samples attributed to the Democratic People’s Republic of Korea, a shared networking infrastructure, and other revealing data hidden within the binaries. Together these puzzle pieces show the connections between the many attacks attributed to North Korea and categorize different tools used by specific teams of their cyber army.

Valuable context 

This article is too short to dig deeply into the history, politics, and economic changes of recent years. Nonetheless, we must highlight some events to put past and present cyber events into perspective.

The DPRK, like any country, wants to be as self-sufficient and independent as possible. However, for products such as oil, food, and foreign currency for trading, the country lacks resources and has to find ways of acquiring them. What can a nation do when legal international economics are denied? To survive, it must gain foreign currency for trading. One of the oldest ways to do this is to join the worlds of gambling (casinos) and drugs. In 2005, the United States wanted to shut down North Korean enterprises involved in illegal operations. They investigated a couple of banks in Asia that seemed to have ties with North Korea and operated as money laundering sites. One bank in particular is controlled by a billionaire gambling mogul who started a casino in Pyongyang and has close ties to Pyongyang. That bank, based in Macau, came back into the picture during an attack on the SWIFT financial system of a bank in Vietnam in 2015. The Macau bank was listed twice in the malware’s code as a recipient of stolen funds:

Figure 1: SWIFT code in malware.

Code reuse

There are many reasons to reuse malware code, which is very common in the world of cybercrime. If we take an average ransomware campaign, for example, once the campaign becomes less successful, actors often change some of basics such as using a different packer to bypass defenses. With targeted campaigns, an adversary must keep its tools undetected for as long as possible. By identifying reused code, we gain valuable insights about the “ancestral relations” to known threat actors or other campaigns. Our research was heavily focused on this type of analysis.

In our years of investigating cyber threats, we have seen the DPRK conduct multiple cyber campaigns. In North Korea, hackers’ skills determine which cyber units they work for. We are aware two major focuses of DPRK campaigns: one to raise money, and one to pursue nationalist aims. The first workforce gathers money for the nation, even if that means committing cybercrime to hack into financial institutions, hijack gambling sessions, or sell pirated and cracked software. Unit 180 is responsible for illegally gaining foreign currency using hacking techniques. The second workforce operates larger campaigns motivated by nationalism, gathering intelligence from other nations, and in some cases disrupting rival states and military targets. Most of these actions are executed by Unit 121.

We focused in our research on the larger-scale nationalism-motivated campaigns, in which we discovered many overlaps in code reuse. We are highly confident that nation-state–sponsored groups were active in these efforts.


We created a timeline of most of the malware samples and noticeable campaigns that we examined. We used primarily open-source blogs and papers to build this timeline and used the malware artifacts as a starting point of our research.


Figure 2: Timeline of malware and campaigns.

Analysis and observations


During our research, we found many malware family names that are believed to be associated with North Korea’s cyber operations. To better understand this threat actor and the similarities between the campaigns, we have used Intezer’s code similarity detection engine to plot the links between a vast number of these malware families.

The following graph presents a high-level overview of these relations. Each node represents a malware family or a hacking tool (“Brambul,” “Fallchill,” etc.) and each line presents a code similarity between two families. A thicker line correlates to a stronger similarity. In defining similarities, we take into account only unique code connections, and disregard common code or libraries. This definition holds both for this graph and our entire research.


Figure 3: Code similarities between North Korean–associated malware families.

We can easily see a significant amount of code similarities between almost every one of the attacks associated with North Korea. Our research included thousands of samples, mostly unclassified or uncategorized. This graph was plotted using a data set of only several hundred samples, so there might be more connections than displayed here. 

Deep technical analysis 

During our research, we came across many code similarities between North Korean binaries that had not been seen before. Some of these attacks and malware have not been linked to one another, at least publicly. We will showcase four examples of reused code that has been seen only in malware attributed to North Korea.

  1. Common SMB module

The first code example appeared in the server message block (SMB) module of WannaCry in 2017, Mydoom in 2009, Joanap, and DeltaAlfa. Further shared code across these families is an AES library from CodeProject. These attacks have been attributed to Lazarus; that means the group has reused code from at least 2009 to 2017.

Figure 4: Code overlap of a Mydoom sample.

In the next screenshots we highlight the exact code block that reflects the SMB module we found in campaigns other than WannaCry and Mydoom.

Figure 5: An SMB module common to several attacks.

A lot has been written about WannaCry. As we analyze the code against our databases, we can draw the following overview:

Figure 6: WannaCry code comparison overview.

For our research we compared the three major variants of WannaCry. An early release, called a beta, from February 2017, one from April, and the infamous one that hit the world in May.

  1. Common file mapping

The second example demonstrates code responsible for mapping a file and using the XOR key 0xDEADBEEF on the first four bytes of the file. This code has appeared in the malware families NavRAT and Gold Dragon, plus a certain DLL from the South Korean gambling hacking campaign. These three RATs are thought to be affiliated with North Korea’s Group 123. NavRAT and the gambling DLL share more code, making them closer variants.

Figure 7: Code overlap in a NavRAT sample.

Figure 8: File-mapping code 

  1. Unique net share

The third example, responsible for launching a cmd.exe with a net share, has been seen in 2009’s Brambul, also known as SierraBravo, as well as KorDllBot in 2011. These malware families are also attributed to the Lazarus group.

Figure 9: Code overlap of a SierraBravo (Brambul) sample.

Figure 10: A code block reused in the malware families Brambul/SierraBravo and KorDllBot.

  1. Operation Dark Hotel

In 2014, Kaspersky reported a more than seven-year campaign against Asian hotels, in which the adversaries used an arsenal of tools to break into the computers of hotel visitors. Zero days and control servers were used, along with the malware family Tapaoux, or DarkHotel, according to the report.

While we examined the DPRK samples, we noticed a hit with the Dark Hotel samples in our collections. By going through the code, we noticed several pieces of code overlap and reuse, for example, with samples from Operation Troy.

Figure 11: Code overlap in a Dark Hotel sample.

Identifying a group

By applying what we learned from our comparisons and code-block identifications, we uncovered possible new links between malware families and the groups using them.

With the different pieces of malware we have analyzed, we can illustrate the code reuse and sharing between the groups known to be affiliated with North Korea.


Figure 12: Groups and families linked by code reuse.

The malware attributed to the group Lazarus has code connections that link many of the malware families spotted over the years. Lazarus is a collective name for many DPRK cyber operations, and we clearly see links between malware families used in different campaigns.

The malware (NavRAT, gambling, and Gold Dragon) possibly created by Group 123 are connected to each other but are separate from those used by Lazarus. Although these are different units focusing on different areas, there seems to be a parallel structure in which they collaborate during certain campaigns.


From our research of these malware samples, we can identify the following techniques used by the malware families:

When we zoom in on the Discovery category in the MITRE model, for example, we notice that the techniques are typical for first-stage dropper malware. The adversary drops these samples on victims’ machines and collects information on where they landed in the victims’ networks and which user/access rights they gained.

In 2018, we saw examples of campaigns in which attackers used PowerShell to download and execute these droppers. Once information has been sent to a control server, the adversary determines the next steps, which often include installing a remote access tool to enable lateral movement on the network and pursue the goals of the campaign.

Final words

Security vendors and researchers often use different names when speaking about the same malware, group, or attack. This habit makes it challenging to group all the malware and campaigns. By taking a scientific approach, such as looking for code reuse, we can categorize our findings. We believe our research will help the security community organize the current “mess” we face in relation to North Korean malware and campaigns.

We clearly saw a lot of code reuse over the many years of cyber campaigns we examined. This indicates the North Koreans have groups with different skills and tools that execute their focused parts of cyber operations while also working in parallel when large campaigns require a mix of skills and tools.

We found our months of research, data gathering, and analysis very satisfying. By combining our skills, data, and technology, we were able to draw connections and reveal links that we had not seen before. The cybersecurity industry would greatly benefit from more collaboration and sharing of information, and we hope that this effort between McAfee and Intezer will inspire the community to work together more often.

The authors thank Costin Raiu for providing them with samples they did not have in their collections.


Glenn Simpson, Gordon Fairclough, and Jay Solomon, “U.S. Probes Banks’ North Korea Ties.” Wall Street Journal, last updated September 8, 2005.

Christiaan Beek, “Attacks on SWIFT Banking system benefit from insider knowledge.”

Atif Mushtaq, “DDOS Madness Continued…”

Ryan Sherstobitoff and Jessica Saavedra-Morales, “Gold Dragon Widens Olympics Malware Attacks, Gains Permanent Presence on Victims’ Systems.” 

Alex Drozhzhin, “Darkhotel: a spy campaign in luxury Asian hotels.” 

Warren Mercer, Paul Rascagneres, and Jungsoo An, “NavRAT Uses US-North Korea Summit As Decoy For Attacks In South Korea.” 

Sergei Shevchenko and Adrian Nish, “Cyber Heist Attribution.

Mydoom code reuse report.

NavRAT code reuse report.

SierraBravo code reuse report.

Dark Hotel code reuse report.

Kang Jang-ho, “A foreign currency earned with a virtual currency … What is the life of a North Korean hacker?”

Awesome work by the team responsible for the “Operation Blockbuster” report.

The post Examining Code Reuse Reveals Undiscovered Links Among North Korea’s Malware Families appeared first on McAfee Blogs.

May 23 2018

VPNFilter Botnet Targets Networking Devices

VPNFilter is a botnet with capabilities to support both intelligence collection and destructive cyberattack operations. The Cisco Talos team recently notified members of the Cyber Threat Alliance (CTA) of its findings and published this blog.

The malware is believed to target networking devices, although the malware’s initial infection vector is still unclear. Talos, which first reported this attack, claims that it has impacted at least 500,000 networking devices during the last few years. The malware can persist on infected devices and can steal website credentials and monitor Modbus SCADA protocols. It also implements file collection, command execution, data extraction, and device management and, even worse, it can render some or all of the infected devices unusable.

The known devices affected by VPNFilter are some network-attached storage (NAS) devices such as Linksys, MikroTik, Netgear, and TP-Link networking equipment in the small and home office (SOHO) space, as well at QNAP.

Malware infection stages

VPNFilter has a three-stage infection.

Stage 1 completes the persistence on the system and uses multiple control mechanisms to find and connect the Stage 2 deployment server.

Stage 2 focuses on file collection, command execution, data extraction, and device management. Some versions possess a self-destruct capability to render itself unusable.

Stage 3 includes two known modules:

  • A traffic sniffer to steal website credentials and monitor Modbus SCADA protocols
  • Tor to communicate with anonymous addresses 

Indicators of compromise and sample hashes

URLs and IPs



File hashes

  • First-Stage Malware
    • 50ac4fcd3fbc8abcaa766449841b3a0a684b3e217fc40935f1ac22c34c58a9ec
    • 0e0094d9bd396a6594da8e21911a3982cd737b445f591581560d766755097d92
  • Second-Stage Malware
    • 9683b04123d7e9fe4c8c26c69b09c2233f7e1440f828837422ce330040782d17
    • d6097e942dd0fdc1fb28ec1814780e6ecc169ec6d24f9954e71954eedbc4c70e
    • 4b03288e9e44d214426a02327223b5e516b1ea29ce72fa25a2fcef9aa65c4b0b
    • 9eb6c779dbad1b717caa462d8e040852759436ed79cc2172692339bc62432387
    • 37e29b0ea7a9b97597385a12f525e13c3a7d02ba4161a6946f2a7d978cc045b4
    • 776cb9a7a9f5afbaffdd4dbd052c6420030b2c7c3058c1455e0a79df0e6f7a1d
    • 8a20dc9538d639623878a3d3d18d88da8b635ea52e5e2d0c2cce4a8c5a703db1
    • 0649fda8888d701eb2f91e6e0a05a2e2be714f564497c44a3813082ef8ff250b
  • Third-Stage Malware
    • f8286e29faa67ec765ae0244862f6b7914fcdde10423f96595cb84ad5cc6b344
    • afd281639e26a717aead65b1886f98d6d6c258736016023b4e59de30b7348719

Coverage and mitigation

The aforementioned IOCs are covered as follows:

  • Detection names for files: Linux/VPNFilter and Linux/VPNFilter.a
    • V3 DAT with coverage version: 3353
    • V2 DAT with coverage version: 8902
  • All samples are GTI classified as malware
  • All relevant URLs are GTI classified

Further recommendations from the Talos threat research team:

  • Reboot SOHO routers and NAS devices to remove the potentially destructive, nonpersistent Stage 2 and Stage 3 malware
  • Work with the manufacturer to ensure that your device is up to date with the latest patches. Apply the updated patches immediately.

ISPs should work aggressively with their customers to ensure their devices are patched to the most recent firmware/

The post VPNFilter Botnet Targets Networking Devices appeared first on McAfee Blogs.

Apr 25 2018

Global Malware Campaign Pilfers Data from Critical Infrastructure, Entertainment, Finance, Health Care, and Other Industries

McAfee Advanced Threat Research analysts have uncovered a global data reconnaissance campaign assaulting a wide number of industries including critical infrastructure, entertainment, finance, health care, and telecommunications. This campaign, dubbed Operation GhostSecret, leverages multiple implants, tools, and malware variants associated with the state-sponsored cyber group Hidden Cobra. The infrastructure currently remains active. (For an extensive analysis by the Advanced Threat Research team, see “Analyzing Operation GhostSecret: Attack Seeks to Steal Data Worldwide.”

The campaign is extremely complicated, leveraging a number of implants to steal information from infected systems and is intricately designed to evade detection and deceive forensic investigators. The implants vary considerably and although they share some functionality and code, they are categorized as different families. As McAfee Advanced Threat Research analysts investigated this campaign, we recognized many similarities to indicators used in the 2014 Sony Pictures attack.

A portion of this campaign aimed at the Turkish financial sector using the Bankshot implant was recently discovered by McAfee Advanced Threat Research analysts. This appears to have been the initial stage of Operation GhostSecret, as within days of publication, new attacks appeared  beyond the financial sector. Between March 14 and 18, we observed the data reconnaissance implant in organizations across 17 countries.

Delving further into this campaign reveals a narrow list of organizations across the globe; the threat actors have been explicit about who can connect from which IP address. Reviewing the WHOIS information for these IP addresses shows us that there is some correlation in geography, although there are no additional clues why these addresses were used.

As we monitor this campaign, it is clear that the publicity associated with the (we assume) first phase of this campaign did nothing to slow the attacks. The threat actors not only continued but also increased the scope of the attack, both in types of targets and in the tools they used. We try to avoid using the word sophisticated because it is both subjective and overused. Nonetheless, the attackers have significant capabilities, demonstrated by their tools development and the pace at which they operate.

Fighting cybercrime is a global effort best undertaken through effective partnerships between the public and private sectors. McAfee is working with Thai government authorities to take down the control server infrastructure of Operation GhostSecret, while preserving the systems involved for further analysis by law enforcement authorities. By creating and maintaining partnerships with worldwide law enforcement, McAfee demonstrates that we are stronger together.

The post Global Malware Campaign Pilfers Data from Critical Infrastructure, Entertainment, Finance, Health Care, and Other Industries appeared first on McAfee Blogs.

Apr 25 2018

Analyzing Operation GhostSecret: Attack Seeks to Steal Data Worldwide

McAfee Advanced Threat Research analysts have uncovered a global data reconnaissance campaign assaulting a wide number of industries including critical infrastructure, entertainment, finance, health care, and telecommunications. This campaign, dubbed Operation GhostSecret, leverages multiple implants, tools, and malware variants associated with the state-sponsored cyber group Hidden Cobra. The infrastructure currently remains active. In this post, we dive deeply into this campaign. For a brief overview of this threat, see “Global Malware Campaign Pilfers Data from Critical Infrastructure, Entertainment, Finance, Health Care, and Other Industries.”

Our investigation into this campaign reveals that the actor used multiple malware implants, including an unknown implant with capabilities similar to Bankshot. From March 18 to 26 we observed the malware operating in multiple areas of the world. This new variant resembles parts of the Destover malware, which was used in the 2014 Sony Pictures attack.

Furthermore, the Advanced Threat Research team has discovered Proxysvc, which appears to be an undocumented implant. We have also uncovered additional control servers that are still active and associated with these new implants. Based on our analysis of public and private information from submissions, along with product telemetry, it appears Proxysvc was used alongside the 2017 Destover variant and has operated undetected since mid-2017.

The attackers behind Operation GhostSecret used a similar infrastructure to earlier threats, including SSL certificates used by FakeTLS in implants found in the Destover backdoor variant known as Escad, which was used in the Sony Pictures attack. Based on our technical analysis, telemetry, and data from submissions, we can assert with high confidence that this is the work of the Hidden Cobra group. The Advanced Threat Research team uncovered activity related to this campaign in March 2018, when the actors targeted Turkish banks. These initial findings appear to be the first stage of Operation GhostSecret. For more on the global aspect of this threat, see “Global Malware Campaign Pilfers Data from Critical Infrastructure of Entertainment, Finance, Health Care, and Other Industries.”


The McAfee Advanced Threat Research team discovered a previously unknown data-gathering implant that surfaced in mid-February 2018. This implant appears to be a derivative of implants authored before by Hidden Cobra and contains functionality similar to that of Bankshot, with code overlaps from other Hidden Cobra implants. However, the variant is not based on Bankshot. Our analysis of the portable executable’s rich-header data reveals that the two implants were compiled in different development environments. (The PE rich header is an undocumented part of a Windows executable that reveals unique information to identify the Microsoft compiler and linker used to create the program. It is helpful for identifying similarities between malware variants to establish common development environments.) Our analysis of the code and PE rich header indicates that Bankshot, Proxysvc, and the Destover-like implant are distinct families, but also contain overlapping code and functionality with current tools of Hidden Cobra.

PE rich header data from the 2018 Bankshot implant.

PE rich header data from the new February 2018 implant.

PE rich header data from Proxysvc.dll.

When we compared the PE rich header data of the new February 2018 implant with a variant of Backdoor.Escad (Destover) from 2014 shortly before the Sony Pictures attack, we found the signatures to be identical. The Destover-like variant is 83% similar in code to a 2015 variant and contains the same rich PE header signature as the Backdoor.Escad variant we analyzed. Thus the new implant is likely a derivative of components of Destover. We determined that the implant is not a direct copy of well-known previous samples of Destover; rather, Hidden Cobra created a new hybrid variant using functionality present in earlier versions.

2014 Backdoor.Escad (hash: 8a7621dba2e88e32c02fe0889d2796a0c7cb5144).

2015 Destover variant (7fe373376e0357624a1d21cd803ce62aa86738b6).

The February implant fe887fcab66d7d7f79f05e0266c0649f0114ba7c was obtained from an unknown submitter in the United States on February 14, two days after it was compiled. This Korean-language file used the control server IP address The implant is nearly identical to an unknown 2017 sample (8f2918c721511536d8c72144eabaf685ddc21a35) except that the control server addresses are different. The 2017 sample used address Both implants specifically use FakeTLS with PolarSSL, which we saw in previous Hidden Cobra implants. PolarSSL libraries have appeared in implants since the Sony Pictures incident and were used exclusively in the implant Backdoor.Destover. This implant incorporated a custom control server protocol that sends traffic over port 443. The implementation does not format the packets in standard SSL, but rather in a custom format and transmitted over SSL—hence, FakeTLS. The control server traffic when compared to Backdoor.Escad is nearly identical.

TLS traffic in Backdoor.Destover, the 2018 Destover-like variant.

TLS traffic in Backdoor.Escad.

Further research into IP address leads us to additional hidden components involved in the overall infrastructure. Proxysvc.dll contains a list of hardcoded IP addresses, including the preceding address, all located in India. Despite the name, this component is not an SSL proxy, but rather a unique data-gathering and implant-installation component that listens on port 443 for inbound control server connections.

Proxysvc was first collected by public and private sources on March 22 from an unknown entity in the United States. The executable dropper for the component was submitted from South Korea on March 19. McAfee telemetry analysis from March 16 to 21 reveals that Proxysvc components were active in the wild. Our research shows this listener component appeared mostly in higher education organizations. We suspect this component is involved in core control server infrastructure. These targets were chosen intentionally to run Proxysvc because the attacker would have needed to know which systems were infected to connect to them. This data also indicates this infrastructure had been operating for more than a year before its discovery. The Advanced Threat Research team found this component running on systems in 11 countries. Given the limited capabilities of Proxysvc, it appears to be part of a covert network of SSL listeners that allow the attackers to gather data and install more complex implants or additional infrastructure. The SSL listener supports multiple control server connections, rather than a list of hardcoded addresses. By removing the dependency on hardcoded IP addresses and accepting only inbound connections, the control service can remain unknown.

The number of infected systems by country in which Proxysvc.dll was operating in March. Source: McAfee Advanced Threat Research.

The 2018 Destover-like implant appeared in organizations in 17 countries between March 14 and March 18. The impacted organizations are in industries such as telecommunications, health, finance, critical infrastructure, and entertainment.

The number of infected systems by country in which the Destover variant was operating in March. Source: McAfee Advanced Threat Research.


Control Servers

Further investigation into the control server infrastructure reveals the SSL certificate d0cb9b2d4809575e1bc1f4657e0eb56f307c7a76, which is tied to the control server, used by the February 2018 implant. This server resides at Thammasat University in Bangkok, Thailand. The same entity hosted the control server for the Sony Pictures implants. This SSL certificate has been used in Hidden Cobra operations since the Sony Pictures attack. Analyzing this certificate reveals additional control servers using the same PolarSSL certificate. Further analysis of McAfee telemetry data reveals several IP addresses that are active, two within the same network block as the 2018 Destover-like implant.

Number of infections by Thammasat Universityhosted control servers from March 1519, 2018. Source: McAfee Advanced Threat Research.

Implant Origins

McAfee Advanced Threat Research determined that the Destover-like variant originated from code developed in 2015. The code reappeared in variants surfacing in 2017 and 2018 using nearly the same functionality and with some modifications to commands, along with an identical development environment based on the rich PE header information.

Both implants (fe887fcab66d7d7f79f05e0266c0649f0114ba7c and 8f2918c721511536d8c72144eabaf685ddc21a35) are based on the 2015 code. When comparing the implant 7fe373376e0357624a1d21cd803ce62aa86738b6, compiled on August 8, 2015, we found it 83% similar to the implant from 2018. The key similarities and differences follow.


  • Both variants build their API imports dynamically using GetProcAddress, including wtsapi32.dll for gathering user and domain names for any active remote sessions
  • Both variants contain a variety of functionalities based on command IDs issued by the control servers
  • Common capabilities of both malware:
    • Listing files in directory
    • Creating arbitrary processes
    • Writing data received from control servers to files on disk
    • Gathering information for all drives
    • Gathering process times for all processes
    • Sending the contents of a specific file to the control server
    • Wiping and deleting files on disk
    • Setting the current working directory for the implant
    • Sending disk space information to the control server
  • Both variants use a batch file mechanism to delete their binaries from the system
  • Both variants run commands on the system, log output to a temporary file, and send the contents of the file to their control servers


The following capabilities in the 2015 implant are missing from the 2018 variant:

  • Creating a process as a specific user
  • Terminating a specific process
  • Deleting a specific file
  • Setting file times for a specific file
  • Getting current system time and sending it to the control server
  • Reading the contents of a file on disk. If the filepath specified is a directory, then listing the directory’s contents.
  • Setting attributes on files

The 2015 implant does not contain a hardcoded value of the IP address it must connect to. Instead it contains a hardcoded sockaddr_in data structure (positioned at 0x270 bytes before the end of the binary) used by the connect() API to specify port 443 and control server IP addresses:


Both of these control servers used the PolarSSL certificate d0cb9b2d4809575e1bc1f4657e0eb56f307c7a76.


At first glance Proxysvc, the SSL listener, looks like a proxy setup tool (to carry out man-in-the-middle traffic interception). However, a closer analysis of the sample reveals it is yet another implant using HTTP over SSL to receive commands from the control server.

Proxysvc appears to be a downloader whose primary capability is to deliver additional payloads to the endpoint without divulging the control address of the attackers. This implant contains a limited set of capabilities for reconnaissance and subsequent payload installations. This implant is a service DLL that can also run as a standalone process.

The ServiceMain() sub function of Proxysvc.

The implant cannot connect to a control server IP address or URL. Instead it accepts commands from the control server. The implant binds and listens to port 443 for any incoming connections. 



Proxysvc binding itself to the specified port.

Proxysvc begins accepting incoming requests to process. 

Proxysvc makes an interesting check while accepting connections from a potential control server. It checks against a list of IP addresses to make sure the incoming connection is not from any of the following addresses. If the incoming request does come from one of these, the implant offers a zero response (ASCII “0”) and shuts down the connection.


SSL Listener Capabilities

The implant receives HTTP-based commands from a control server and parses the HTTP Content-Type and Content-Length from the HTTP header. If the HTTP Content-Type matches the following value, then the implant executes the command specified by the control server:

Content-Type: 8U7y3Ju387mVp49A

HTTP Content-Type comparison with a custom implant value.

The implant has the following capabilities:

  • Writing an executable received from the control server into a temp file and executing it

Proxysvc writing a binary to a temp directory and executing it. 

  • Gathering system information and sending it to the control server. The system information gathered from the endpoint includes:
    • MAC address of the endpoint
    • Computer Name
    • Product name from HKLM\Software\Microsoft\Windows NT\CurrentVersion ProductName
    • This information is concatenated into a single string in the format: “MAC_Address|ComputerName|ProductName” and is sent to the control server
  • Recording HTTP requests from the control server to the temporary file prx in the implant’s install directory with the current system timestamp

Analyzing the Main Implant

The February 2018 implant contains a wide variety of capabilities including data exfiltration and arbitrary command execution on the victim’s system. Given the extensive command structure that the implant can receive from the control server, this is an extensive framework for data reconnaissance and exfiltration, and indicates advanced use. For example, the implant can wipe and delete files, execute additional implants, read data out of files, etc.

The implant begins execution by dynamically loading APIs to perform malicious activities. Libraries used to load the APIs include:

  • Kernel32.dll
  • Apvapi32.dll
  • Oleaut32.dll
  • Iphlpapi.dll
  • Ws2_32.dll
  • Wtsapi32.dll
  • Userenv.dll
  • Ntdll.dll

The main implant dynamically loading APIs.

As part of its initialization, the implant gathers basic system information and sends it to its hardcoded control server using SSL over port 443:

  • Country name from system’s locale
  • Operating system version
  • Processor description from

HKLM\HARDWARE\DESCRIPTION\System\CentralProcessor\0 ProcessorNameString

  • Computer name and network adapters information
  • Disk space information for disks C: through Z: including total memory in bytes, total available memory in bytes, etc.
  • Current memory status including total physical memory in bytes, total available memory, etc.
  • Domain name and usernames based on current remote sessions

Domain name and username extraction using Win32 WTS APIs.

Data Reconnaissance

The implant receives commands over SSL as encoded data. This data is decoded, and the correct command ID is derived. Valid command IDs reside between 0 and 0x1D.

Switch case handling command execution based on command IDs.

Based on the command ID, the implant can perform the following functions:

  • Gather system information and exfiltrate to the control server (same as the basic data-gathering functionality previously described)
  • Get volume information for all drives on the system (A: through Z:) and exfiltrate to the control server

Gathering volume information.

  • List files in a directory. The directory path is specified by the control server.
  • Read the contents of a file and send it to the control server

Reading file contents and sending it the control server.

  • Write data sent by the control server to a specified file path

Open handle to a file for writing with no shared permissions.

Writing data received from control server to file.

  • Create new processes based on the file path specified by the control server.

Creating a new process for a binary specified by the control server.

  • Wipe and delete files specified by the control server

Wiping and deleting files.

  • Execute a binary on the system using cmd.exe and log the results into a temp file, which is then read and the logged results are sent to the control server. The command line:

cmd.exe /c “<file_path> > %temp%\PM*.tmp 2>&1”

Executing a command and logging results to a temp file.

  • Get information for all currently running processes

Getting process times for all processes on the system.

Getting username and domain from accounts associated with a running process.

  • Delete itself from disk using a batch file.

Creating a batch file for self-deletion.

  • Store encoded data received from the control server as a registry value at:

HKLM\Software\Microsoft\Windows\CurrentVersion\TowConfigs Description

  • Set and get the current working directory for the implant

Setting and getting the current working directory for the implant’s process.

The command handler index table is organized in the implant as follows:

The command handler index table.


This analysis by the McAfee Advanced Threat Research team has found previously undiscovered components that we attribute to Hidden Cobra, which continues to target organizations around the world. The evolution in complexity of these data-gathering implants reveals an advanced capability by an attacker that continues its development of tools. Our investigation uncovered an unknown infrastructure connected to recent operations with servers in India using an advanced implant to establish a covert network to gather data and launch further attacks.

The McAfee Advanced Threat Research team will provide further updates as our investigation develops.

Fighting cybercrime is a global effort best undertaken through effective partnerships between the public and private sectors. McAfee is working with Thai government authorities to take down the control server infrastructure of Operation GhostSecret, while preserving the systems involved for further analysis by law enforcement authorities. By creating and maintaining partnerships with worldwide law enforcement, McAfee demonstrates that we are stronger together.  

Indicators of Compromise

McAfee detection

  • Trojan-Bankshot2

MITRE ATT&CK techniques

  • Exfiltration over control server channel: data is exfiltrated over the control server channel using a custom protocol
  • Commonly used port: the attackers used common ports such as port 443 for control server communications
  • Service execution: registers the implant as a service on the victim’s machine
  • Automated collection: the implant automatically collects data about the victim and sends it to the control server
  • Data from local system: local system is discovered and data is gathered
  • Process discovery: implants can list processes running on the system
  • System time discovery: part of the data reconnaissance method, the system time is also sent to the control server
  • File deletion: malware can wipe files indicated by the attacker

IP addresses



  • fe887fcab66d7d7f79f05e0266c0649f0114ba7c
  • 8f2918c721511536d8c72144eabaf685ddc21a35
  • 33ffbc8d6850794fa3b7bccb7b1aa1289e6eaa45 

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