Security researchers have discovered the sophisticated Triada Trojan in the firmware of more than 40 low-cost Android smartphone models.
Discovered in early 2016 and considered one of the most advanced mobile threats out there, Triada stands out in the crowd because it abuses the Zygote parent process to inject its code in the context of all software on the device. The Trojan uses root privileges to replace system files and resides mainly in the device’s RAM, which makes it difficult to detect.
In April last year, security researchers discovered that Triada had adopted sandbox technology in an attempt to boost its detection evasion capabilities. Specifically, the malware was using the open source sandbox DroidPlugin, which allowed it to dynamically load and run code going through the installation process.
Several months later, in July 2017, Doctor Web reported that Triada was present in the firmware of several low-cost Android smartphones. At the time, the list of infected device models included Leagoo M5 Plus, Leagoo M8, Nomu S10, and Nomu S20.
Now, the security firm reveals that the Trojan comes pre-installed on a larger number of Android smartphone models, even on devices that were launched in December 2017. Overall, over 40 device models were found to be impacted, the security researchers say.
The specific malware variant found on these devices is detected as Android.Triada.231 and includes all of the capabilities a member of the Triada family comes with: it injects its module in the Zygote process to penetrate all running applications on the device.
This allows the Trojan to carry out a broad range of malicious activities without user interaction, such as covertly downloading and launching applications. Designed with a modular architecture, Triada can redirect financial SMS transactions to buy additional content or steal money from the user.
Because the malware authors managed to inject Android.Triada.231 into the libandroid_runtime.so system library, they are able to compromise a device’s firmware during the manufacturing process, and users end up receiving smartphones that have been already infected.
Doctor Web says they notified manufacturers who produced infected devices of the compromise last year, but infected models continue to be produced. One of these is the Leagoo M9 smartphone, which was announced in December 2017.
“Additionally, our analysts’ research showed that the Trojan’s penetration into firmware happened at request of the Leagoo partner, the software developer from Shanghai. This company provided Leagoo with one of its applications to be included into an image of the mobile operating system, as well as with an instruction to add third-party code into the system libraries before their compilation,” Doctor Web says.
Despite this controversial request, the manufacturer didn’t become suspicious and the Trojan ended up on the new smartphone model without any obstacles.
The security researchers also discovered that the malicious application was signed with the same certificate as Android.MulDrop.924, a Trojan discovered in 2016. This suggests that the developer requesting the addition of the code into the mobile operating system image might be involved in the distribution of Triada.
Doctor Web published a list of the 40 device models infected with Triada, but warns that the list might not be comprehensive, as other compromised smartphones could exist out there. Impacted manufacturers include Leagoo, ARK, Zopo, Doogee, Vertex, Advan, Cubot, Prestigio, Pelitt, and more.
“Such widespread distribution of Android.Triada.231 shows that many Android device manufacturers pay little attention to security questions and penetration of the Trojan code into system components. This can be due to error or malicious intent and is likely common practice,” the researchers point out.
Related: Triada Trojan Preinstalled on Low-Cost Android Devices