Blog details

19 Sep

Executive Summary

  • SentinelLabs identified three Android application packages (APK) linked to Transparent Tribe’s CapraRAT mobile remote access trojan (RAT).
  • These apps mimic the appearance of YouTube, though they are less fully featured than the legitimate native Android YouTube application.
  • CapraRAT is a highly invasive tool that gives the attacker control over much of the data on the Android devices that it infects.

Background

Transparent Tribe is a suspected Pakistani actor known for targeting military and diplomatic personnel in both India and Pakistan, with a more recent expansion to the Indian Education sector. Since 2018, reports have detailed the group’s use of what is now called CapraRAT, an Android framework that hides RAT features inside of another application. The toolset has been used for surveillance against spear-phishing targets privy to affairs involving the disputed region of Kashmir, as well as human rights activists working on matters related to Pakistan.

Transparent Tribe distributes Android apps outside of the Google Play Store, relying on self-run websites and social engineering to entice users to install a weaponized application. Earlier in 2023, the group distributed CapraRAT Android apps disguised as a dating service that conducted spyware activity.

One of the newly identified APKs reaches out to a YouTube channel belonging to Piya Sharma, which has several short clips of a woman in various locales. This APK also borrows the individual’s name and likeness. This theme suggests that the actor continues to use romance-based social engineering techniques to convince targets to install the applications, and that Piya Sharma is a related persona.

CapraRAT is a comprehensive RAT that provides the actors with the ability to harvest data on demand and exfiltrate it. Notable features include:

  • Recording with the microphone, front & rear cameras
  • Collecting SMS and multimedia message contents, call logs
  • Sending SMS messages, blocking incoming SMS
  • Initiating phone calls
  • Taking screen captures
  • Overriding system settings such as GPS & Network
  • Modifying files on the phone’s filesystem

App Analysis

CapraRAT is distributed as an Android APK. When the tool was initially named by Trend Micro, their research team noted that CapraRAT may be loosely based on the AndroRAT source code.

We performed static analysis on two YouTube-themed CapraRAT APKs: 8beab9e454b5283e892aeca6bca9afb608fa8718 – yt.apk, uploaded to VirusTotal in July 2023. 83412f9d757937f2719ebd7e5f509956ab43c3ce – YouTube_052647.apk, uploaded to VirusTotal in August 2023. We also identified a third APK called Piya Sharma, the YouTube channel persona described earlier: 14110facecceb016c694f04814b5e504dc6cde61 – Piya Sharma.apk, uploaded to VirusTotal in April 2023

The yt and YouTube APKs apps are disguised as YouTube, borrowing the YouTube icon.

Applications icons on an Android device, including YouTube_052647.apk
Applications icons on an Android device, including YouTube_052647.apk
Application icons, including the Piya Sharma app
Application icons, including the Piya Sharma app
YouTube_052647.apk displays the YouTube website when launched
YouTube_052647.apk displays the YouTube website when launched

The app requests several permissions. YouTube is an interesting choice for masquerading the app: some permissions, like microphone access, make sense for recording or search features. Other permissions–like the ability to send and view SMS–are less relevant to the expected app behaviors.

Permissions prompts during install of the weaponized YouTube app
Permissions prompts during install of the weaponized YouTube app

Installation permissions requested by the Piya Sharma APK
Installation permissions requested by the Piya Sharma APK

When the app is launched, MainActivity’s load_web method launches a WebView object to load YouTube’s website. Because this loads within the trojanized CapraRAT app’s window, the user experience is different from the native YouTube app for Android and akin to viewing the YouTube page in a mobile web browser.

Smali snippet of the load_web method in MainActivity
Smali snippet of the load_web method in MainActivity

Key Components

Because CapraRAT is a framework inserted into a variety of Android applications, the files housing malicious activity are often named and arranged differently depending on the app. The CapraRAT APKs we analyzed contain the following files:

Name yt.apk
Configuration com/media/gallery/service/settings
Version MSK-2023
Main com/media/gallery/service/MainActivity
Malicious Activity com/media/gallery/service/TPSClient
Name YouTube_052647.apk
Configuration com/Base/media/service/setting
Version A.F.U.3
Main com/Base/media/service/MainActivity
Malicious Activity com/Base/media/service/TCHPClient
Name Piya Sharma.apk
Configuration com/videos/watchs/share/setting
Version V.U.H.3
Main com/videos/watchs/share/MainActivity
Malicious Activity com/videos/watchs/share/TCPClient

CapraRAT’s configuration file, which is named interchangeably setting or settings, holds the default configuration information, as well as metadata like versioning. The CapraRAT version syntax seen in YouTube_052647.apk and Piya Sharma.apk–A.F.U.3 and V.U.H.3, respectively–matches the convention used to track Transparent Tribe’s Windows tool, CrimsonRAT. However, there is no tangible relationship between these version numbers and the C2 domains as we saw in CrimsonRAT.

Thanks to creative spelling and naming conventions, the RAT’s configuration provides consistent static detection opportunities, with each of the following present in the samples from earlier in 2023 as well:


 	is_phical
 	isCancl
 	isRealNotif
 	SERVERIP
 	smsMoniter
 	smsWhere
 	verion

MainActivity is responsible for driving the application’s key features. This activity sets persistence through the onCreate method which uses Autostarter, an open-source project with code that lets developers automatically launch an Android application. The TPSClient class is initialized as an object called mTCPService; then, this method calls the serviceRefresh method, which creates an alarm at the interval specified in the settings file’s timeForAlarm variable. In this example, the value 0xea60 is equal to 60,000 milliseconds, meaning the alarm and persistence launcher run once per minute.

The RAT’s core functionality is in an activity similar to the Extra_Class activity from the March 2023 samples reported by ESET. Henceforth, we call this activity TPSClient for simplicity. These files are rather large, decompiling to over 10,000 lines of Smali code. By comparison, the March versions’ equivalents have only about 8,000 lines.

TPSClient contains CapraRAT’s commands, which are invoked through the run method via a series of switch statements that map the string command to a related method.

The smsmons command logic inside the run method of TPSClient
The smsmons command logic inside the run method of TPSClient

Many of these commands have been documented in previous research, though there are several changes in these new versions. The hideApp method now checks if the system is running Android version 9 or earlier and if the mehiden variable in the setting(s) config file was set to False; if applicable, the app will be hidden from the user’s view. While similarities between CapraRAT and AndroRAT are seemingly minimal at this point in CapraRAT’s development, the AndroRAT source code documentation notes that the tool becomes unstable after Android version 9, so there are likely underlying changes to the OS that make this method behave differently depending on the OS version.

TPSClient has a method check_permissions() that is not in Extra_Class. This method checks the following series of Android permissions and generates a string with a True or False result for each:

  • READ_EXTERNAL_STORAGE
  • READ_CALL_LOG
  • CAMERA
  • READ_CONTACTS
  • ACCESS_FINE_LOCATION
  • RECORD_AUDIO
  • READ_PHONE_STATE

Interestingly, some other older versions contain this method, suggesting that the samples may be tailored for targets or are potentially developed from different branches.

C2 & Infrastructure

In CapraRAT’s configuration file, the SERVERIP variable contains the command-and-control (C2) server address, which can be a domain, IP address, or both. The C2 port is in hexadecimal Big Endian format; the human readable port can be obtained by converting into decimal, resulting in port 14862 for yt.apk, port 18892 for YouTube_052647.apk, and port 10284 for Piya Sharma.apk.

C2 configuration from yt.apk (left) and YouTube_052647.apk (right)
C2 configuration from yt.apk (left) and YouTube_052647.apk (right)

The shareboxs[.]net domain used by YouTube_052647.apk has been associated with Transparent Tribe since at least 2019. Interestingly, the ptzbubble[.]shop domain was registered the same week of ESET’s report outlining the group’s Android apps that leveraged other C2 domains.

The IP addresses associated with C2 from the two YouTube samples have Remote Desktop Protocol port 3389 open with the service identified as Windows Remote Desktop, indicating the group uses Windows Server infrastructure to host the CapraRAT C2 application. The Piya Sharma app’s C2 IP, 209[.]127.19.241, has a certificate with common name value WIN-P9NRMH5G6M8, a longstanding indicator associated with Transparent Tribe’s CrimsonRAT C2 servers.

84[.]46.251.145–the IP address hosting ptzbubble[.]shop domain–shows historical resolutions associated with Decoy Dog Pupy RAT DNS tunneling lookups. Any connection between these campaigns is unclear; it is plausible that a service hosted on this IP was infected by that campaign. Based on the query dates, the claudfront[.]net lookup was during the time the CapraRAT actor was using this IP address to host ptzbubble[.]shop, while a lookup to allowlisted[.]net was in December 2022, which was potentially before this actor started using the IP.

Resolution history for IP hosting ptzbubble[.]shop, 84[.]46.251.145
Resolution history for IP hosting ptzbubble[.]shop, 84[.]46.251.145

Conclusion

Transparent Tribe is a perennial actor with reliable habits. The relatively low operational security bar enables swift identification of their tools.

The group’s decision to make a YouTube-like app is a new addition to a known trend of the group weaponizing Android applications with spyware and distributing them to targets through social media.

Individuals and organizations connected to diplomatic, military, or activist matters in the India and Pakistan regions should evaluate defense against this actor and threat.

Defensive and preventative measures should include:

  • Do not install Android applications outside of the Google Play store.
  • Be wary of new social media applications advertised within social media communities.
  • Evaluate the permissions requested by an application, particularly an application you are not particularly familiar with. Do these permissions expose you to more risk than the potential benefit of the app?
  • Do not install a third-party version of an application already on your device.

Indicators of Compromise (IOC)

Files Hashes – SHA1
14110facecceb016c694f04814b5e504dc6cde61 – Piya Sharma APK
83412f9d757937f2719ebd7e5f509956ab43c3ce – CapraRAT, YouTube_052647.apk
8beab9e454b5283e892aeca6bca9afb608fa8718 – CapraRAT, yt.apk

C2 Network Communications
newsbizshow.net
ptzbubble.shop
shareboxs.net

95[.]111.247.73
209[.]127.19.241

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