A malicious modified version of WhatsApp for Android has been observed spreading the Triada mobile Trojan, which can download additional malware, launch ads, issue subscriptions, and intercept a victim's SMS messages.
Users of the messaging platform often aren't satisfied with its feature set, explain Kaspersky researchers who discovered the malicious modification. These users want additional capabilities, such as animated themes, automatic translation, or self-destructing messages, and will turn to modified, amateur-designed versions of WhatsApp that contain them.
Researchers report the Trojan Triada snuck into one of these modified versions, called FMWhatsapp 16.80.0, together with the advertising software development kit (SDK). The creators of modified app versions often publish ads to monetize their work, researchers note.
When the app is downloaded and launched, the malware collects device identifiers, such as device ID, subscriber ID, and MAC address, and the name of the app package where it's deployed. Then, at the owner's command, the Trojan downloads another Trojan to the device. This Trojan can launch adds, issue paid subscriptions to the device owner, and log into their WhatsApp account.
"With this app, it is hard for users to recognize the potential threat because the mod application actually does what is proposed – it adds additional features," said Igor Golovin, security expert as Kaspersky, in a statement. "However, we have observed how cybercriminals have started to spread malicious files through the ad blocks in such apps."
He advises only using messenger software downloaded from legitimate app stores.
Read the full blog post for more details.