Sunday, March 3, 2024

BadBazaar espionage software targets Android customers through trojanized Sign and Telegram apps

ESET researchers have recognized two energetic campaigns focusing on Android customers, the place the menace actors behind the software are attributed to the China-aligned APT group GREF. Most certainly energetic since July 2020 and since July 2022, respectively, the campaigns have distributed the Android BadBazaar espionage code by means of the Google Play retailer, Samsung Galaxy Retailer, and devoted web sites representing the malicious apps Sign Plus Messenger and FlyGram. The menace actors patched the open-source Sign and Telegram apps for Android with malicious code that we’ve got recognized as BadBazaar.

Key factors of the report:

  • ESET Analysis found trojanized Sign and Telegram apps for Android, known as Sign Plus Messenger and FlyGram, on Google Play and Samsung Galaxy Retailer; each apps have been later faraway from Google Play.
  • The malicious code present in these apps is attributed to the BadBazaar malware household, which has been used up to now by a China-aligned APT group known as GREF.
  • BadBazaar malware has beforehand been used to focus on Uyghurs and different Turkic ethnic minorities. FlyGram malware was additionally seen shared in a Uyghur Telegram group, which aligns with earlier focusing on of the BadBazaar malware household.
  • FlyGram can entry Telegram backups if the person enabled a particular characteristic added by the attackers; the characteristic was activated by no less than 13,953 person accounts.
  • Sign Plus Messenger represents the primary documented case of spying on a sufferer’s Sign communications by secretly autolinking the compromised machine to the attacker’s Sign machine.

Primarily based on our telemetry, we have been capable of establish energetic Android campaigns the place an attacker uploaded and distributed malicious apps that go by the names Sign Plus Messenger and FlyGram through the Google Play retailer, Samsung Galaxy Retailer, and devoted web sites, mimicking the Sign utility (signalplus[.]org) and a Telegram different app (flygram[.]org).

The aim of those trojanized apps is to exfiltrate person knowledge. Particularly, FlyGram can extract primary machine info, but additionally delicate knowledge, resembling contact lists, name logs, and the record of Google Accounts. Furthermore, the app is able to exfiltrating some info and settings associated to Telegram; nevertheless, this knowledge doesn’t embody the Telegram contact record, messages, or every other delicate info. Nonetheless, if customers allow a particular FlyGram characteristic that permits them to again up and restore Telegram knowledge to a distant server managed by the attackers, the menace actor could have full entry to those Telegram backups, not solely the collected metadata. It is very important observe that these backups don’t include precise messages. Throughout the evaluation of this characteristic, we realized that the server assigns a singular ID to each newly created person account. This ID follows a sequential sample, indicating {that a} minimal of 13,953 FlyGram accounts had activated this characteristic.

Sign Plus Messenger collects comparable machine knowledge and delicate info; its major aim, nevertheless, is to spy on the sufferer’s Sign communications – it might extract the Sign PIN quantity that protects the Sign account, and misuses the hyperlink machine characteristic that permits customers to hyperlink Sign Desktop and Sign iPad to their telephones. This spying method stands out as a consequence of its uniqueness, because it differs from the performance of every other recognized malware.

The video above exhibits how the menace actor hyperlinks the compromised machine to the attacker’s Sign account with none person interplay; it additionally explains how customers can verify whether or not their Sign account has been linked to a different machine.

As a Google App Protection Alliance accomplice, ESET recognized the latest model of the Sign Plus Messenger as malicious and promptly shared its findings with Google. Following our alert, the app was faraway from the shop. FlyGram wasn’t flagged as malicious by ESET on the time when it initially grew to become accessible on the Google Play retailer.

On April 27th, 2023, we reported Sign Plus Messenger to each Google Play and Samsung Galaxy Retailer. Google took motion and eliminated the app on Could 23rd, 2023. FlyGram was taken down from Google Play someday after January 6th, 2021. On the time of writing, each apps are nonetheless accessible on the Samsung Galaxy Retailer.


The malicious Sign Plus Messenger app was initially uploaded to Google Play on July 7th, 2022, and it managed to get put in greater than 100 occasions. Nonetheless, the Galaxy Retailer doesn’t present any details about the app’s preliminary add date or the variety of installations. Its presence on each platforms is depicted in Determine 1.

BadBazaar Figure_01
Determine 1. Sign Plus Messenger accessible on Google Play (left) and Samsung Galaxy Retailer (proper)

Each apps have been created by the identical developer, share the identical malicious options, and the app descriptions on each shops confer with the identical developer web site, signalplus[.]org. The area was registered on February 15th, 2022, and gives a hyperlink to obtain the malicious Sign Plus Messenger utility both from Google Play or immediately from the web site, as proven in Determine 2. No matter the place the app is downloaded from – be it the Google Play model, the Samsung Galaxy Retailer model, or the web site model – all three downloads end in acquiring a maliciously modified (or patched) model of the open-source Sign for Android app.

BadBazaar Figure_01
Determine 2. Distribution web site of the malicious Sign Plus Messenger app

The malicious FlyGram app was initially uploaded to Google Mess around June 4th, 2020, and it managed to garner greater than 5,000 installations earlier than being taken down someday after January 6th, 2021.

Each FlyGram apps have been signed utilizing the an identical code-signing certificates. Furthermore, the identical FlyGram app can also be accessible for obtain from its devoted web site flygram[.]org. This web site was registered on April 6th, 2020, and gives a hyperlink to obtain the malicious FlyGram utility immediately from the web site, as you possibly can see in Determine 3.


BadBazaar Figure_03
Determine 3. The malicious FlyGram app accessible for obtain on Galaxy Retailer (left) and a devoted web site (proper)

Primarily based on code similarities, we will assign Sign Plus Messenger and FlyGram to the BadBazaar malware household, which has been beforehand used in opposition to Uyghurs and different Turkic ethnic minorities outdoors of China. BadBazaar was attributed to the China-aligned APT15 group by Lookout; beneath we clarify why we restrict attribution to the GREF group, and why we’re at present unable to hyperlink GREF to APT15, however proceed to watch the scenario. Additional particulars in regards to the BadBazaar discovery timeline can be found in Determine 4.

BadBazaar Figure_04
Determine 4. BadBazaar discovery timeline


Our telemetry reported detections on Android units from Australia, Brazil, Denmark, the Democratic Republic of the Congo, Germany, Hong Kong, Hungary, Lithuania, the Netherlands, Poland, Portugal, Singapore, Spain, Ukraine, america, and Yemen.

BadBazaar Figure 05
Determine 5. Detection telemetry

Primarily based on our analysis, aside from distribution from the official Google Play retailer and Samsung Galaxy Retailer, potential victims have been additionally lured to put in the FlyGram app from a Uyghur Telegram group targeted on Android app sharing, which now has greater than 1,300 members.

On July 26th, 2020, one of many group customers posted a hyperlink to FlyGram on the Google Play retailer with an outline to obtain a multilanguage Telegram app, as proven in Determine 6. This would possibly assist to establish who focused Uyghurs with the malicious FlyGram utility.

BadBazaar Figure_06
Determine 6. Hyperlink to obtain FlyGram posted in a Uyghur Telegram group

Primarily based on accessible info on official app shops, we will’t inform who has been focused by the marketing campaign, for the reason that apps have been accessible for obtain with out area restrictions.

Attribution to GREF

  • Important code similarities between the Sign Plus Messenger and FlyGram samples, and the BadBazaar malware household, which Lookout attributes to the GREF cluster of APT15. To one of the best of our information, this malware household is exclusive to GREF.
  • Overlap within the focusing on: the malicious FlyGram app used a Uyghur Telegram group as one of many distribution mechanisms. This aligns with the focusing on of different Android trojans beforehand utilized by GREF (BadBazaar, SilkBean, DoubleAgent, CarbonSteal, and GoldenEagle).
BadBazaar Figure_07
Determine 7. Code that gathers machine data: BadBazaar pattern found by Lookout (left) and Sign Plus Messenger (proper)
Determine 8. Malicious code liable for gathering Wi-Fi data from BadBazaar (left) and FlyGram (proper)

Sign Plus Messenger and FlyGram additionally include the identical code as in BadBazaar to verify whether or not the machine operator is Chinese language: see Determine 9.

Determine 9. Code liable for figuring out whether or not the machine operator is Chinese language

Technical evaluation

Each Sign Plus Messenger and FlyGram are barely totally different variants of BadBazaar that target person knowledge exfiltration and espionage. Nonetheless, it’s essential to notice that every of them possesses distinctive malicious functionalities. To make sure readability and keep away from any confusion, we are going to analyze every variant individually.

Trojanized Sign – Sign Plus Messenger app

After preliminary app begin, the person has to log into Sign Plus Messenger through authentic Sign performance, identical to they’d with the official Sign app for Android. As soon as logged in, Sign Plus Messenger begins to speak with its command and management (C&C) server, positioned at signalplus[.]org:4332. Throughout this communication, the app sends the server varied machine info, resembling: IMEI quantity, telephone quantity, MAC deal with, operator particulars, location knowledge, Wi-Fi info, Sign PIN quantity that protects the account (if enabled by the person), emails for Google accounts, and make contact with record. The server request is seen in Determine 10.


Determine 10. BadBazaar uploads machine info to its C&C server

Legit Sign apps present a characteristic that permits customers to hyperlink Sign Desktop and Sign iPad to their telephones to speak conveniently throughout a number of units. To correctly hyperlink further Sign units to a smartphone, the person first must scan a QR code displayed on a tool they want to pair. After scanning, the person grants permission for the connection by tapping on the Hyperlink machine button, as displayed in Determine 11. The QR code comprises a singular URI with a generated ID and key, making certain safe and individualized linking for every new QR code. An instance of such URI is sgnl://linkdevice?uuid=<redacted>fV2MLK3P_FLFJ4HOpA&pub_key=<redacted>1cCVJIyt2uPJK4fWvXt0m6XEBN02qJG7pcpercent2BmvQa.

BadBazaar Figure_01
Determine 11. Consumer wants to verify machine linking

Sign Plus Messenger can spy on Sign messages by misusing the hyperlink machine characteristic. It does this by mechanically connecting the compromised machine to the attacker’s Sign machine. This methodology of spying is exclusive, as we haven’t seen this performance being misused earlier than by different malware, and that is the one methodology by which the attacker can receive the content material of Sign messages.

BadBazaar, the malware liable for the spying, bypasses the standard QR code scan and person click on course of by receiving the required URI from its C&C server, and immediately triggering the required motion when the Hyperlink machine button is clicked. This permits the malware to secretly hyperlink the sufferer’s smartphone to the attacker’s machine, permitting them to spy on Sign communications with out the sufferer’s information, as illustrated in Determine 12.


BadBazaar Figure_01
Determine 12. Mechanism of linking the sufferer’s Sign communications to the attacker

ESET Analysis has knowledgeable Sign’s builders about this loophole. The encrypted messaging service indicated that menace actors can alter the code of any messaging app and put it on the market in a misleading or deceptive method. On this case, if the official Sign purchasers have been to show a notification at any time when a brand new machine is linked to the account, the faux model might merely disable that code path to bypass the warning and conceal any maliciously linked units. The one method to forestall changing into a sufferer of a faux Sign – or every other malicious messaging app – is to obtain solely official variations of such apps, solely from official channels.

Throughout our analysis, the server hasn’t returned to the machine a URI for linking, indicating that is probably enabled just for particularly focused customers, based mostly on the information beforehand despatched by the malware to the C&C server.

To know and replicate the conduct, we used the Frida instrumentation toolkit to simulate malicious conduct and autolinked our compromised Sign Android machine (sufferer) to our Sign Desktop machine (attacker), working on a laptop computer. This linking course of occurred silently, with none interplay or notification to the person.

To make sure that a Sign account shouldn’t be linked to a different machine, the person must go to Settings -> Linked units. This gives a means for customers to detect any unauthorized linkages to their Sign account and take acceptable actions to safe their communications, as BadBazaar can’t cover an attacker-connected machine from the Linked units menu, as depicted in Determine 13.


BadBazaar Figure_01
Determine 13. Checklist of linked units

BadBazaar makes use of proxy servers which can be acquired from the C&C server. The malware can obtain as much as six totally different proxy servers, which confer with subdomains of the C&C server.

All proxy servers offered by Sign Plus Messenger are:

  • proxy1.signalplus[.]org    154.202.59[.]169
  • proxy2.signalplus[.]org    92.118.189[.]164
  • proxy3.signalplus[.]org    45.154.12[.]151
  • proxy4.signalplus[.]org    45.154.12[.]202
  • proxy5.signalplus[.]org    103.27.186[.]195
  • proxy6.signalplus[.]org    103.27.186[.]156

The characteristic to make use of a proxy server by the app shouldn’t be applied by the attacker; as an alternative, authentic Sign proxy performance is used however routed by means of the attacker’s server as an alternative. Consequently, the attacker’s proxy server can presumably log some metadata, however can’t decrypt knowledge and messages which can be despatched or acquired by Sign itself.

Trojanized Telegram – FlyGram app

After preliminary app launch, the person has to log into the FlyGram app through its authentic Telegram performance, as is important for the official Telegram app. Earlier than the login is full, FlyGram begins to speak with the C&C server positioned at flygram[.]org:4432 by sending primary machine info resembling: IMEI quantity, MAC deal with, operator title, machine language, and time zone. Primarily based on the server’s response, BadBazaar positive aspects the flexibility to exfiltrate additional delicate info from the machine, together with:

  • contact record,
  • name logs,
  • record of put in apps,
  • record of Google accounts,
  • machine location, and
  • Wi-Fi info (IP deal with, SSID, BSSID, MAC deal with, gateway, DNS, native community machine scan discovery).

FlyGram also can obtain a URL from the C&C server to obtain an replace; see Determine 14. The downloaded replace (flygram.apk) shouldn’t be dynamically loaded as a further payload, however must be manually put in by the person. Throughout our examination, we have been unable to entry the replace file because the obtain hyperlink was not energetic.

BadBazaar Figure_01
Determine 14. Server response with URL hyperlink to FlyGram replace

BadBazaar can exfiltrate inner Telegram information positioned within the /knowledge/knowledge/org.telegram.messenger/shared_prefs listing. These information include info and settings associated to Telegram, such because the account token, the final known as quantity, and the app language. Nonetheless, they don’t embody the Telegram contact record, messages, or every other delicate knowledge.

To hold out the exfiltration course of, BadBazaar compresses the content material of this listing, excluding information with .jpg or .png extensions. The compressed knowledge is then saved within the file /knowledge/knowledge/org.telegram.FlyGram/cache/tgmcache/tgdata.rc. Lastly, the malware sends this compressed file to the C&C server, as proven in Determine 15.

BadBazaar Figure_01
Determine 15. Code snippet liable for itemizing information within the shared_prefs listing

The BadBazaar actors took steps to guard their FlyGram app from being intercepted throughout community visitors evaluation by malware analysts or automated sandbox instruments that try and establish the C&C server and knowledge exfiltration actions. They achieved this safety by means of a way known as SSL pinning.

SSL pinning is applied within the org.telegram.Api.Utils.CertUtils class, as proven in Determine 16. The certificates is saved within the assets listing of the APK file, particularly within the /res/uncooked/telemon_client.cer file utilizing WMSvc-WIN-50QO3EIRQVP because the widespread title (CN). This SSL pinning mechanism ensures that solely encrypted communication with the predefined certificates is allowed, making it tough for outsiders to intercept and analyze the community visitors between the FlyGram app and its C&C server. In distinction, the Sign Plus Messenger app doesn’t make use of SSL pinning, which suggests it doesn’t have this particular degree of safety in place.


BadBazaar Figure_01
Determine 16. SSL pinning applied by BadBazaar

On prime of its authentic Telegram performance, FlyGram builders applied a Cloud Sync characteristic that permits the customers to again up and restore Telegram contacts, profile photos, teams, channels, and so forth. (see Determine 17). To make use of this characteristic, the person first must create an account. The account is created utilizing the attacker’s C&C server API (flygram[.]org:4432); as soon as the account is about up, customers can add their backups to the attacker’s C&C server or retrieve their earlier backups from there.


BadBazaar Figure_01
Determine 17. Cloud Sync login display screen (left) and account sync interface (proper)

Throughout our in-depth examination of the Cloud Sync API, we made an fascinating discovery. The server gives a definite ID for every newly created person account. This ID is a singular worth that will increase sequentially (by one) with every new account. By analyzing these ID values, we will estimate the variety of customers who’ve put in FlyGram and signed up for the Cloud Sync characteristic. On the time of our evaluation, our final check account was assigned the ID worth 13,953 (see Determine 18), indicating that at the moment 13,953 customers (together with us two occasions) had created accounts with the Cloud Sync characteristic enabled.


BadBazaar Figure_01
Determine 18. C&C server response returns person knowledge with ID

FlyGram additionally makes use of proxy servers acquired from the C&C server; we noticed these 5 proxy servers:

  • 45.63.89[.]238:1011
  • 45.133.238[.]92:6023
  • 217.163.29[.]84:7011
  • 185.239.227[.]14:3023
  • 62.210.28[.]116:2011

To allow the proxy server performance, the attackers didn’t implement it immediately into the app. As a substitute, they utilized the authentic Telegram performance however rerouted it by means of their very own servers. Consequently, the attacker’s proxy server could possibly log some metadata, however it can’t decrypt the precise knowledge and messages exchanged inside Telegram itself. Not like Sign Plus Messenger, FlyGram lacks the flexibility to hyperlink a Telegram account to the attacker or intercept the encrypted communications of its victims.


Two energetic Android campaigns operated by the GREF APT group distributed Android malware known as BadBazaar through two apps, by means of the official Google Play retailer, and nonetheless distributes it through Samsung Galaxy Retailer, different app shops, and devoted web sites. A hyperlink to FlyGram within the Google Play retailer was additionally shared in a Uyghur Telegram group. Malicious code from the BadBazaar household was hidden in trojanized Sign and Telegram apps, which ought to present victims a working app expertise (with out cause to take away it) however with espionage occurring within the background.

BadBazaar’s major goal is to exfiltrate machine info, the contact record, name logs, and the record of put in apps, and to conduct espionage on Sign messages by secretly linking the sufferer’s Sign Plus Messenger app to the attacker’s machine.

For any inquiries about our analysis revealed on WeLiveSecurity, please contact us at
ESET Analysis presents non-public APT intelligence reviews and knowledge feeds. For any inquiries about this service, go to the ESET Menace Intelligence web page.




Bundle title

ESET detection title





BadBazaar malware.




BadBazaar malware from Google Play retailer.




BadBazaar malware from Samsung Galaxy Retailer.




BadBazaar malware from distribution web site and Samsung Galaxy Retailer.




BadBazaar malware from Google Play retailer.




Internet hosting supplier

First seen



The Fixed Firm, LLC


FlyGram proxy server.





FlyGram proxy server.





C&C server.





Sign Plus proxy server.





Sign Plus proxy server.





FlyGram proxy server.



Hostinger Worldwide Restricted


Distribution web site.





Sign Plus proxy server.



Starry Community Restricted


Sign Plus proxy server.



Starry Community Restricted


Sign Plus proxy server.



Hetzner On-line GmbH – Contact Function, ORG-HOA1-RIPE


C&C server.





Sign Plus proxy server.



Hostinger Worldwide Restricted


Distribution web site.



Starry Community Restricted


FlyGram proxy server.



Abuse-C Function


FlyGram proxy server.

This desk was constructed utilizing model 13 of the MITRE ATT&CK framework.








Software program Discovery

BadBazaar can receive an inventory of put in purposes.


System Community Configuration Discovery

BadBazaar can extract IMEI, IMSI, IP deal with, telephone quantity, and nation.


System Data Discovery

BadBazaar can extract details about the machine, together with SIM serial quantity, machine ID, and customary system info.



Knowledge from Native System

BadBazaar can exfiltrate information from a tool.


Location Monitoring

BadBazaar tracks machine location.


Protected Consumer Knowledge: Name Logs

BadBazaar can extract name logs.


Protected Consumer Knowledge: Contact Checklist

BadBazaar can extract the machine’s contact record.



BadBazaar can hyperlink the sufferer’s Sign account to a tool the attacker controls and intercept communications.

Command and Management


Utility Layer Protocol: Internet Protocols

BadBazaar makes use of HTTPS to speak with its C&C server.


Non-Customary Port

BadBazaar communicates with its C&C server utilizing HTTPS requests over port 4332 or 4432.



Exfiltration Over C2 Channel

BadBazaar exfiltrates knowledge utilizing HTTPS.



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