ESET researchers analyze a cyberespionage campaign that distributes CapraRAT backdoors through trojanized and supposedly secure Android messaging apps – but also exfiltrates sensitive information
ESET researchers have identified an active Transparent Tribe campaign, targeting mostly Indian and Pakistani Android users – presumably with a military or political orientation. Victims were probably targeted through a honey-trap romance scam, where they were initially contacted on another platform and then convinced to use supposedly “more secure” apps, which they were then lured into installing. Most likely active since July 2022, the campaign has distributed CapraRAT backdoors through at least two similar websites, while representing them as untainted versions of those secure messaging apps.
Besides the inherent working chat functionality of the original legitimate app, the trojanized versions include malicious code that we have identified as that of the CapraRAT backdoor. Transparent Tribe, also known as APT36, is a cyberespionage group known to use CapraRAT; we have also seen similar baits deployed against its targets in the past. The backdoor is capable of taking screenshots and photos, recording phone calls and surrounding audio, and exfiltrating any other sensitive information. The backdoor can also receive commands to download files, make calls, and send SMS messages. The campaign is narrowly targeted, and nothing suggests these apps were ever available on Google Play. We identified this campaign when analyzing a sample posted on Twitter that was of interest due to matching Snort rules for both CrimsonRAT and AndroRAT. Snort rules identify and alert on malicious network traffic and can be written to detect a specific type of attack or malware. CrimsonRAT is Windows malware, known to be used only by Transparent Tribe. In 2021, the group started to target the Android platform, using a modified version of an open-source RAT named AndroRAT. It bears similarities to CrimsonRAT, and has been named CapraRAT by Trend Micro in its research. Based on the Android Package Kit (APK) name, the first malicious application is branded MeetsApp and claims to provide secure chat communications. We were able to find a website from which this sample could have been downloaded (meetsapp[.]org); see Figure 1. Figure 1. Distribution website of CapraRAT posing as MeetsApp That page’s download button leads to an Android app with the same name; unfortunately, the download link is not alive anymore (https://phone-drive[.]online/download.php?file=MeetsApp.apk). At the time of this research, phone-drive[.]online resolved to 198.37.123[.]126, which is the same IP address as phone-drive.online.geo-news[.]tv, which was used in the past by Transparent Tribe to host its spyware. Analysis of the MeetsApp distribution website showed that some of its resources were hosted on another server with a similar domain name – meetup-chat[.]com – using a similar service name. That site also provided an Android messaging app, MeetUp, to download with the same package name (com.meetup.app) as for MeetsApp, and having the same website logo, as can be seen in Figure 2. Figure 2. Distribution website of CapraRAT posing as MeetUp Both apps – from the tweet and from the sample downloaded from meetup-chat[.]com – include the same CapraRAT code, communicate with the same C&C server (66.235.175[.]91:4098), and their APK files are signed using the same developer certificate. Hence, we strongly believe that both websites were created by the same threat actor; both domains were registered around the same time – July 9th and July 25th, 2022. Both apps are based on the same legitimate code trojanized with CapraRAT backdoor code. Messaging functionality seems either to be developed by the threat actor or found (maybe purchased) online, since we couldn’t identify its origin. Before using the app, victims need to create accounts that are linked to their phone numbers and require SMS verification. Once this account is created, the app requests further permissions that allow the backdoor’s full functionality to work, such as accessing contacts, call logs, SMS messages, external storage, and recording audio. The domain phone-drive[.]online on which the malicious MeetsApp APK was placed started to resolve to the same IP address around the same time as the domain phone-drive.online.geo-news[.]tv that was used in the past campaign controlled by Transparent Tribe, as reported by Cisco. Besides that, the malicious code of the analyzed samples was seen in the previous campaign reported by Trend Micro where CapraRAT was used. In Figure 3 you can see a comparison of malicious class names from CapraRAT available from 2022-01 on left side, and its more recent variant having the same class names and functionality. Figure 3. Malicious class name comparison of older CapraRAT (left) and more recent version (right) During our investigation, weak operational security resulted in the exposure of some victim data. This information allowed us to geolocate over 150 victims in India, Pakistan, Russia, Oman, and Egypt, as seen in Figure 4. Figure 4. Victim distribution Based on our research, potential victims were lured to install the app by a honey-trap romance scam operation, where most likely they were first contacted on a different platform and then persuaded to use the “more secure” MeetsApp or MeetUp app. We have previously seen such baits being used by Transparent Tribe operators against their targets. Finding a mobile number or an email address they can use to make first contact is usually not difficult. As described above, the malicious MeetUp app has been available at meetup-chat[.]com, and we believe with high confidence that the malicious MeetsApp was available at meetsapp[.]org. Neither app would be automatically installed from these locations; the victims had to choose to download and install the apps manually. Considering that only a handful individuals were compromised, we believe that potential victims were highly targeted and lured using romance schemes, with Transparent Tribe operators most likely establishing first contact via another messaging platform. After gaining the victims’ trust, they suggested moving to another – allegedly more secure – chat app that was available on one of the malicious distribution websites. There was no subterfuge suggesting the app was available in Google Play. After the victim signs into the app, CapraRAT then starts to interact with its C&C server by sending basic device info and waits to receive commands to execute. Based on these commands, CapraRAT is capable of exfiltrating: It can also receive commands to download a file, launch any installed app, kill any running app, make a call, send SMS messages, intercept received SMS messages, and download an update and request the victim to install it. The mobile campaign operated by Transparent Tribe is still active, representing itself as two messaging applications, used as a cover to distribute its Android CapraRAT backdoor. Both apps are distributed through two similar websites that, based on their descriptions, provide secure messaging and calling services. Transparent Tribe probably uses romance scam baits to lure victims into installing the app and continues to communicate with them using the malicious app to keep them on the platform and make their devices accessible to the attacker. CapraRAT is remotely controlled and based on the commands from the C&C server, it can exfiltrate any sensitive information from its victims’ devices. Operators of these apps had poor operational security, resulting in victim PII being exposed to our researchers, across the open internet. Because of that, it was possible to obtain some information about the victims. This table was built using version 12 of the MITRE ATT&CK framework.Key points of the blogpost:
Campaign overview
MeetsApp
MeetUp
Attribution to Transparent Tribe
Victimology
Technical analysis
Initial access
Toolset
Conclusion
ESET Research offers private APT intelligence reports and data feeds. For any inquiries about this service, visit the ESET Threat Intelligence page.IoCs
Files
SHA-1 Package name ESET detection name Description
4C6741660AFED4A0E68EF622AA1598D903C10A01 com.meetup.chat Android/Spy.CapraRAT.A CapraRAT backdoor.
542A2BC469E617252F60925AE1F3D3AB0C1F53B6 com.meetup.chat Android/Spy.CapraRAT.A CapraRAT backdoor.
Network
IP Provider First seen Details
66.235.175[.]91 N/A 2022-09-23 C&C.
34.102.136[.]180 GoDaddy 2022-07-27 meetsapp[.]org – distribution website.
194.233.70[.]54 123-Reg Limited 2022-07-19 meetup-chat[.]com – distribution website.
198.37.123[.]126 Go Daddy 2022-01-20 phone-drive[.]online – APK file hosted website.
194.233.70[.]54 Mesh Digital Limited 2022-09-23 share-lienk[.]info – APK file hosting website.
MITRE ATT&CK techniques
Tactic ID Name Description
Persistence T1398 Boot or Logon Initialization Scripts CapraRAT receives the BOOT_COMPLETED broadcast intent to activate at device startup.
T1624.001 Event Triggered Execution: Broadcast Receivers CapraRAT functionality is triggered if one of these events occurs: PHONE_STATE, NEW_OUTGOING_CALL, BATTERY_CHANGED, or CONNECTIVITY_CHANGE.
Discovery T1420 File and Directory Discovery CapraRAT can list available files on external storage.
T1424 Process Discovery CapraRAT can obtain a list of running applications.
T1422 System Network Configuration Discovery CapraRAT can extract IMEI, IMSI, IP address, phone number, and country.
T1426 System Information Discovery CapraRAT can extract information about the device including SIM serial number, device ID, and common system information.
Collection T1533 Data from Local System CapraRAT can exfiltrate files from a device.
T1517 Access Notifications CapraRAT can collect notification messages from other apps.
T1512 Video Capture CapraRAT can take photos and exfiltrate them.
T1430 Location Tracking CapraRAT tracks device location.
T1429 Audio Capture CapraRAT can record phone calls and surrounding audio.
T1513 Screen Capture CapraRAT can record the device’s screen using the MediaProjectionManager API.
T1636.002 Protected User Data: Call Logs CapraRAT can extract call logs.
T1636.003 Protected User Data: Contact List CapraRAT can extract the device’s contact list.
T1636.004 Protected User Data: SMS Messages CapraRAT can extract SMS messages.
Command and Control T1616 Call Control CapraRAT can make phone calls.
T1509 Non-Standard Port CapraRAT communicates with its C&C over TCP port 4098.
Impact T1582 SMS Control CapraRAT can send SMS messages.
Discussion