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MalBus: Popular South Korean Bus App Series in Google Play Found Dropping Malware After 5 Years of Development

McAfee’s Mobile Research team recently learned of a new malicious Android application masquerading as a plugin for a transportation application series developed by a South Korean developer. The series provides a range of information for each region of South Korea, such as bus stop locations, bus arrival times and so on. There are a total of four apps in the series, with three of them available from Google Play since 2013 and the other from around 2017. Currently, all four apps have been removed from Google Play while the fake plugin itself was never uploaded to the store. While analyzing the fake plugin, we were looking for initial downloaders and additional payloads – we discovered one specific version of each app in the series (uploaded at the same date) which was dropping malware onto the devices on which they were installed, explaining their removal from Google Play after 5 years of development.

Figure 1. Cached Google Play page of Daegu Bus application, one of the apps in series

When the malicious transportation app is installed, it downloads an additional payload from hacked web servers which includes the fake plugin we originally acquired. After the fake plugin is downloaded and installed, it does something completely different – it acts as a plugin of the transportation application and installs a trojan on the device, trying to phish users to input their Google account password and completely take control of the device. What is interesting is that the malware uses the native library to take over the device and also deletes the library to hide from detection. It uses names of popular South Korean services like Naver, KakaoTalk, Daum and SKT. According to our telemetry data, the number of infected devices was quite low, suggesting that the final payload was installed to only a small group of targets.

The Campaign

The following diagram explains the overall flow from malware distribution to device infection.

Figure 2. Device infection process

When the malicious version of the transportation app is installed, it checks whether the fake plugin is already installed and, if not, downloads from the server and installs it. After that, it downloads and executes an additional native trojan binary which is similar to the trojan which is dropped by the fake plugin. After everything is done, it connects with the C2 servers and handles received commands.

Initial Downloader

The following table shows information about the malicious version of each transportation app in the series. As the Google Play number of install stats shows, these apps have been downloaded on many devices.

Unlike the clean version of the app, the malicious version contains a native library named “libAudio3.0.so”.

Figure 3. Transportation app version with malicious native library embedded

In the BaseMainActivity class of the app, it loads the malicious library and calls startUpdate() and updateApplication().

Figure 4. Malicious library being loaded and executed in the app

startUpdate() checks whether the app is correctly installed by checking for the existence of a specific flag file named “background.png” and whether the fake plugin is installed already. If the device is not already infected, the fake plugin is downloaded from a hacked web server and installed after displaying a toast message to the victim. updateApplication() downloads a native binary from the same hacked server and dynamically loads it. The downloaded file (saved as libSound1.1.so) is then deleted after being loaded into memory and, finally, it executes an exported function which acts as a trojan. As previously explained, this file is similar to the file dropped by the fake plugin which is discussed later in this post.

Figure 5 Additional payload download servers

Fake Plugin

The fake plugin is downloaded from a hacked web server with file extension “.mov” to look like a media file. When it is installed and executed, it displays a toast message saying the plugin was successfully installed (in Korean) and calls a native function named playMovie(). The icon for the fake plugin soon disappears from the screen. The native function implemented in LibMovie.so, which is stored inside the asset folder, drops a malicious trojan to the current running app’s directory masquerading as libpng.2.1.so file. The dropped trojan is originally embedded in the LibMovie.so xor’ed, which is decoded at runtime. After giving permissions, the address of the exported function “Libfunc” in the dropped trojan is dynamically retrieved using dlsym(). The dropped binary in the filesystem is deleted to avoid detection and finally Libfunc is executed.

Figure 6 Toast message when malware is installed

In the other forked process, it tries to access the “naver.property” file on an installed SD Card, if there is one, and if it succeeds, it tries starting “.KaKaoTalk” activity which displays a Google phishing page (more on that in the next section) . The overall flow of the dropper is explained in the following diagram:

Figure 7. Execution flow of the dropper

Following is a snippet of a manifest file showing that “.KaKaoTalk” activity is exported.

Figure 8. Android Manifest defining “.KaKaoTalk” activity as exported

Phishing in JavaScript

KakaoTalk class opens a local HTML file, javapage.html, with the user’s email address registered on the infected device automatically set to log into their account.

Figure 9. KakaoTalk class loads malicious local html file

The victim’s email address is set to the local page through a JavaScript function setEmailAddress after the page is finished loading. A fake Korean Google login website is displayed:

Figure 10. The malicious JavaScript shows crafted Google login page with user account

We found the following attempts of exploitation of Google legitimate services by the malware author:

  • Steal victim’s Google account and password
  • Request password recovery for a specific account
  • Set recovery email address when creating new Google account

An interesting element of the phishing attack is that the malware authors tried to set their own email as the recovery address on Google’s legitimate services. For example, when a user clicks on the new Google account creation link in the phishing page, the crafted link is opened with the malware author’s email address as a parameter of RecoveryEmailAddress.

Figure 11. The crafted JavaScript attempts to set recovery email address for new Google account creation.

Fortunately for end users, none of the above malicious attempts are successful. The parameter with the malware author’s email address is simply ignored at the account creation stage.

Trojan

In addition to the Google phishing page, when “Libfunc” function of the trojan (dropped by the fake plugin or downloaded from the server) is executed, the mobile phone is totally compromised. It receives commands from the following hardcoded list of C2 servers. The main functionality of the trojan is implemented in a function called “doMainProc()”. Please note that there are a few variants of the trojanwith different functionality but, overall, they are pretty much the same.

Figure 12. Hardcoded list of C2 servers

The geolocation of hardcoded C2 servers lookslike the following:

Figure 13. Location of C2 Servers

Inside doMainProc(), the trojan receives commands from the C2 server and calls appropriate handlers. Part of the switch block below gives us an idea of what type of commands this trojan supports.

Figure 14. Subset of command handlers implemented in the dropped trojan.

As you can see, it has all the functionality that a normal trojan has. Downloading, uploading and deleting files on the device, leaking information to a remote server and so on. The following table explains supported C2 commands:

Figure 15. C2 Commands

Before entering the command handling loop, the trojan does some initialization, like sending device information files to the server and checking the UID of the device. Only after the UID checking returns a 1 does it enter the loop.

Figure 16 Servers connected before entering command loop

Among these commands, directory indexing in particular is important. The directory structure is saved in a file named “kakao.property” and while indexing the given path in the user device, it checks the file with specific keywords and if it matches, uploads the file to the remote upload server. These keywords are Korean and its translated English version is as per the following table:

Figure 17 Search file keywords

By looking at the keywords we can anticipate that the malware authors were looking for files related to the military, politics and so on. These files are uploaded to a separate server.

Figure 18 Keyword matching file upload server

Conclusion

Applications can easily trick users into installing them before then leaking sensitive information. Also, it is not uncommon to see malware sneaking onto the official Google Play store, making it hard for users to protect their devices. This malware has not been written for ordinary phishing attempts, but rather very targeted attacks, searching the victim’s devices for files related to the military and politics, likely trying to leak confidential information. Users should always install applications that they can fully trust even though they are downloaded from trusted sources.

McAfee Mobile Security detects this threat as Android/MalBus and alerts mobile users if it is present, while protecting them from any data loss. For more information about McAfee Mobile Security, visit https://www.mcafeemobilesecurity.com.

Hashes (SHA-256)

Initial Downloader (APK)
• 19162b063503105fdc1899f8f653b42d1ff4fcfcdf261f04467fad5f563c0270
• bed3e665d2b5fd53aab19b8a62035a5d9b169817adca8dfb158e3baf71140ceb
• 3252fbcee2d1aff76a9f18b858231adb741d4dc07e803f640dcbbab96db240f9
• e71dc11e8609f6fd84b7af78486b05a6f7a2c75ed49a46026e463e9f86877801

Fake Plugin (APK)
• ecb6603a8cd1354c9be236a3c3e7bf498576ee71f7c5d0a810cb77e1138139ec
• b8b5d82eb25815dd3685630af9e9b0938bccecb3a89ce0ad94324b12d25983f0

Trojan (additional payload)
• b9d9b2e39247744723f72f63888deb191eafa3ffa137a903a474eda5c0c335cf
• 12518eaa24d405debd014863112a3c00a652f3416df27c424310520a8f55b2ec
• 91f8c1f11227ee1d71f096fd97501c17a1361d71b81c3e16bcdabad52bfa5d9f
• 20e6391cf3598a517467cfbc5d327a7bb1248313983cba2b56fd01f8e88bb6b9

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Microsoft Cortana Allows Browser Navigation Without Login: CVE-2018-8253

A locked Windows 10 device with Cortana enabled on the lock screen allows an attacker with physical access to the device to do two kinds of unauthorized browsing. In the first case, the attacker can force Microsoft Edge to navigate to an attacker-controlled URL; in the second, the attacker can use a limited version of Internet Explorer 11 using the saved credentials of the victim.

In June we published our analysis of a full login bypass mechanism for all Windows 10 devices for which Cortana is enabled on the lock screen. (This is still the default option.) The discovery of the full login bypass was part of a wider research effort into what access the digital assistant Cortana might offer to an adversary when the device is locked. This post details these two additional issues; we reported them to Microsoft at the same time we reported the login bypass. The two new flaws have now been addressed as part of Microsoft’s August update. Some of the issues are also partially mitigated by modifying the answer obtained from a Bing search query.

In the first scenario, a Cortana privilege escalation leads to forced navigation on a lock screen. The vulnerability does not allow an attacker to unlock the device, but it does allow someone with physical access to force Edge to navigate to a page of the attacker’s choosing while the device is still locked. This is not a case of BadUSB, man in the middle, or rogue Wi-Fi, just simple voice commands and interacting with the device’s touchscreen or mouse.

Several months ago, researchers from Israel demonstrated a similar attack using a BadUSB device, masquerading as a network interface card to inject content into trusted HTTP sites while using Cortana to force navigation. Microsoft has since removed this ability to navigate directly to a domain and instead now opens a search in Bing over HTTPS to the domain in question. Some of our findings could also be combined with a BadUSB approach.

We explored whether one could still force navigation to an attacker-controlled page. In short, yes, one can, but it does take some extra effort.

Cortana is very helpful when it comes to defining terms, or looking up corporations, movies, artists, or athletes. She can even do math. However, Cortana’s behavior and the answers she gives are affected by the way you ask a question. For example, if you were to ask the colloquial question “Hey Cortana, what is McAfee?” you would get a quick answer directly from a Bing search. If, however, you asked only “Hey Cortana, McAfee,” you would receive a more detailed response, including links to various trusted sites. These include Wikipedia, Twitter, Facebook, LinkedIn, and the “official website” (more later on this important link).

Cortana’s answers to similar but not identical queries about “McAfee.”

It is surprising that links are offered and clickable when the device is locked. If you start your favorite network sniffer or man-in-the-middle proxy, you will see that the links are visited as soon as the user clicks on them, irrespective of the device’s locked status.

This means we can force navigation to a website (though not yet the one we want) when the device is locked. However, we have seen that Cortana can be picky in how she offers results. Bing must already know these results, and most links are known trusted sites.

That leaves us with the official website. You might recognize this terminology: It is a common link presented by Wikipedia. If you look at the bottom of a Wikipedia article, you will often find a link to an official website.

Could Cortana just use Wikipedia as a trusted source? After a few delightful conversations with her, we can confirm that the official website for items she refers from Wikipedia is indeed the same as the Official Website link on Wikipedia. There is no one-to-one correlation on Wikipedia’s official website for Cortana to display the corresponding link. We assume there is some possible weighting of the domain name or logic in the Bing output that influences Cortana’s displayed links.

We can leverage this information to craft a fake Wikipedia entry, add enough content to get the review to succeed, add an official website link, and see what Cortana presents. Wikipedia reviewers do a pretty good job of vetting content, but we also need Bing to become aware of the entry so that Cortana could offer the answer and the link. Because of the time-dependent factor of the approach (and the ethical aspect of tampering with Wikipedia content in a malicious way), we decided to take a different path—although others could use this attack vector.

Instead of creating an entry in Wikipedia, making sure that Bing indexes it and that Cortana provides the official website link, we opted for an alternative. We can instead hunt Wikipedia for unmaintained or dead official website links. Fortunately for us, Wikipedia maintains a list of “dead links” and “permanent dead links.” A search for “Xbox Linux” looks like this:

To aid in our hunt, Wikipedia has a fairly robust search engine that accepts regular expressions.

With just a little bit of tinkering we come up with the following search:

insource:/\{official (website)?\|https?\:\/\/[^}]+\.com\/[^}]\}\}\{\{dead link/

This is neither an exhaustive list, nor the most efficient regular expression, but it does find some candidates without triggering the Wikipedia query timeout.

The next step is to write a script to parse the output, grab a list of domains, and check whether they are actually vacant. Many of them are still registered but do not serve any content; others are live despite the “dead link” tag. We end up with a list of domains, some more expensive than others, that are vacant.

What will Cortana display for each of these Wikipedia entries? One after another, we ask. Retrospectively, writing a text-to-speech script would have been faster. Cortana answers surprisingly well to other digital speech synthesizers.

Many of the entries do not provide the official website link, but some do. It is annoying that the way you ask the question interferes with the results. Not only is the phrasing of the question important; the decision of whether to dictate a word or spell it out may change the answer. To obtain the answer you want from Cortana, you may have to combine both approaches.

For example, we asked “Hey Cortana, what is Miss Aruba?” We saw, while the device was locked, the following answer:

The official website link points to “hxxp://www.missaruba.aw.” A quick search shows the domain is still available.

In conclusion, we now have Wikipedia articles for which Cortana will display an official website link, and for which the domain is available for purchase. After spending $11.99 for a cheaper domain, we own one.

Although it took some regular-expression authoring, some scripting, and buying a domain, this method was faster and more satisfying than waiting for Bing to publish and index a new Wikipedia entry.

After this setup, what can we accomplish? We can ask Cortana (either via the interactive icon or vocal command “Hey Cortana”) to conduct a search while the device is locked. When she replies, we can click on the official website link and observe as Edge retrieves the content while the device remains locked.  To put a malicious spin on this unauthorized access, we have at least one straightforward option. We could install the latest exploit kit on our newly acquired domain and infect any locked Windows 10 PC with Cortana enabled without ever logging in. This attack could occur at a coffee shop, retailer, bank, or against targeted individuals. This configuration is the default on Windows, and our research has shown that many users never disable Cortana from the lock screen.

Digital voice assistants can be useful, but they must also be considered an attack vector. Although some may think this is a “noisy” vector, not applicable when stealth is required, you can employ techniques such as the DolphinAttack, which uses inaudible voice commands to close an air gap. Or if you have physical access to the device, a $5 3.5mm-jack cable will do as well.

An inexpensive 3.5mm-jack cable for silent interaction.

How can we protect against this attack vector? You can disable Cortana on your lock screen. Microsoft should not allow navigation to untrusted websites until it receives permission from the authenticated user, confirming on login that the user wants to visit a site.

Self-service Internet Explorer from the Windows lock screen

When we investigate a technology, we sometimes find that our initial findings are less substantial than what we learn after further investigation. Our research into Cortana and this attack surface was no different. What if one could surf the web freely with a full-fledged browser such as Internet Explorer 11, with access to cached credentials and autocomplete on a locked Windows 10 device? All thanks to Cortana? That could be much more impactful than browsing to just one URL.

That is possible with Cortana’s skills. It makes sense that Cortana offers skills similar to those of Amazon’s Alexa or Google Assistant. But it does not make sense to offer these skills directly from the lock screen when they are not yet configured.

One example is the “Real Estate Search” skill. While conversing with Cortana to analyze the capabilities she could offer an attacker, we found that she occasionally offered to try skills, including Real Estate Search.

One easy trigger is to ask “Hey Cortana, I want to sell my house.” This leads to the following screen:

If we click “Real Estate Search,” we get a login screen. Instead of logging in, let’s look at the other links offered by the interface. In the current case, the “Privacy Policy” link seems interesting:

Cortana’s skill login screen with a link to Privacy Policy.

Opening the link, we see a lengthy policy. If we scroll to the bottom of the page, we discover a few social media icons:

Privacy policy screen with links to social media sites.

These icons are indeed links, allowing us to reach Facebook or YouTube, and from there the rest of the Internet:

Reaching Facebook from the lock screen of a Windows 10 system.

Let’s summarize. You left for lunch with your new Windows Surface Book locked on your desk. Cortana is on by default on your lock screen. Your disk is encrypted. What could go wrong?

Anybody who has physical access to your locked device can start browsing the web. What if someone were to navigate to a work-unfriendly website from your device, or post inflammatory comments in a public forum that could be attributed to your device’s IP address?

A device-specific attribution would be bad, but could you use the same method to post or access something from a real person’s name or account? We next investigated which browser is being used? Is it a Cortana custom browser? Is it a sandboxed Microsoft Edge? It is actually a customized Internet Explorer 11 restricted engine running in the context of AuthHost.exe. (We will publish another analysis on this limited “browser” because its properties and lack of security mechanisms could become handy for red teams.)

This is the Internet Explorer engine and not the full browser, though both JavaScript and cookies are enabled. Worse, this incarnation shares the autocomplete and credentials saved in the context of the current user’s Internet Explorer session.

Thus in addition to posting a comment on a public forum from another user’s device while the device is locked, you can also impersonate the user thanks to its cached credentials.

One potential attack scenario arises if a corporation offers a mechanism to reset Windows credentials via a web server but does not require users to reenter the old password. One could simply navigate to the reset link, input a new password, exit the limited navigator, and unlock the device with the newly set password, all from a locked computer.

We have explored a couple of attack scenarios and security issues in this post, and we will continue our investigation into Cortana and other digital assistants as an attack vector. Your best mitigation at this point is to turn off Cortana on the lock screen. Here is a good tutorial on how to do so.

 

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McAfee Labs – McAfee Blogs 2018-06-19 00:01:25

Every week we read about adversaries attacking their targets as part of online criminal campaigns. Information gathering, strategic advantage, and theft of intellectual property are some of the motivations. Besides these, we have seen during the past two years an increase in attacks in which adversaries are not shy of leaving a trail of destruction. One might wonder how to deal with these kinds of threats and where to start.

Sun Tzu’s The Art of War contains some great wisdom regarding the strategy of warfare. One of the most popular is the advice “If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.”

Applying this advice to information security, let’s focus first on knowing yourself. Knowing yourself can roughly be divided into two parts:

  • What do I have that can be of value to an attacker?
  • How do I detect, protect, and correct any threats to my identified value?

Every company has a value, it takes only one criminal mind to see that and to attempt to exploit it. Ask yourself what the core of your business is, the secret sauce that people might be after, what will take you out of business, whom you are doing business with, who are your clients, etc.

Once you have identified your organization’s value, the second part of knowing yourself comes into play. You must understand where you to focus your defenses and invest in technology to detect and protect against threats.

After wrapping up the knowing yourself part, what can we learn from the enemy? Ask yourself “Who would likely be interested in attacking me?” By going through the list of known adversaries and cybercriminal groups, you can create a list based on which geographies and vectors they target and classify them by risk. Here is a simplified example:

Once you have your list and risk classification ready, you must next study the tactics, techniques, and procedures used by these adversaries. For mapping their techniques and associated campaigns, we use the MITRE Adversarial Tactics, Techniques, and Common Knowledge model (ATT&CK). The matrix covers hundreds of techniques, and can be applied for different purposes. In this case, we will focus on the risk versus mapping the defensive architecture.

In Q1 of 2018, we mapped the targeted attacks discovered by ourselves and our peers in the industry. The following example comes from one adversary we tracked, showing the techniques they used:

With MITRE’s Navigator tool you can select an actor or malware family. After making the selection, the boxes in the matrix show which techniques the actor or malware has used.

From these techniques we can learn how our environments protect against these techniques and where we have gaps. The goal is not to create coverage or signatures for each technique; the matrix helps organizations understand how attackers behave. Having more visibility into their methods leads us to the right responses, and helps us contain and eradicate attacks in a coordinated way. By comparing the multiple actors from your initial risk assessment, you can build the matrix from the perspective of high/medium/low risk and map it against your defenses.

Although some adversaries might not have a history of attacking you and your sector, it is still good to ask yourself “What if we were a target?” Would your environment create enough visibility to detect and deal with these techniques?

Statistics

When we looked at the first quarter, we noticed that the three techniques were the most popular in the category of Privilege Escalation:

  • Exploitation of vulnerability
  • Process injection
  • Valid accounts

To determine your coverage and detection capacity, you should ask if the exploits used completely new vulnerabilities (no patches available) or if they had existed for a while. Would your environment have the right patches installed or are you missing them and have to take action?

When we looked at the categories of Exfiltration and Command and Control, most campaigns exfiltrated their data over a control server channel using a common port. That translates to either TCP port 80 (HTTP) or TCP port 443 (HTTPS). We all use these ports from inside the network to communicate to the internet. What if all my other defenses would fail to discover the suspicious activity? Which defensive components in my network would be able to inspect the outgoing traffic and block or flag the exfiltration attempts?

Conclusion

In this post, we highlighted one approach and application of the ATT&CK model. There are many ways to apply it for red teaming, threat hunting, and other tasks. At McAfee we embrace the model and are applying it to different levels and purposes in our organization. We are not only using it but also contribute to the model by describing newly discovered techniques used by adversaries.

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Unintended Clipboard Paste Function in Windows 10 Leads to Information Leak in RS1

The McAfee Labs Advanced Threat Research team has been investigating the Windows 10 platform. We have submitted several vulnerabilities already and have disclosed our research to Microsoft. Please refer to our vulnerability disclosure policy for further details or the post from earlier this week on Windows 10 Cortana vulnerabilities.

Early last year, a trivial “information leak” was reported in Windows 10. This technique no longer works on most current builds of Windows 10, but a variation of this simple method works quite well on some versions of Windows 10, specifically RS1 (RedStone 1).

The issue is simple to describe and execute. For a local attack, you can use a physical keyboard; if there is a network vector that would allow one to remotely reach the Windows login screen (such as RDP), you can use the software-based keyboard accessible from the lock screen. On all versions of Windows 10, the “paste” function appears to be intentionally forbidden from the Windows lock screen, including the “Hey Cortana” function. The original finding demonstrated CTRL+V could be used to paste clipboard contents. This is now disabled, even on RS1. However, we have found a way to bypass this restriction using the keyboard shortcut CTRL + SHIFT + INSERT, allowing us to access in plain text the clipboard contents, whatever they may be. While we are continuing to explore this technique to force-copy functions (and access arbitrary content), for now we can access whatever happens to be copied. In the demo this is a password allowing login.


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