In another instance of threat actors sneaking malware (opens in new tab)-ridden apps past Google's threat detection filters, cybersecurity (opens in new tab) researchers have revealed that over 300,000 users have downloaded malicious Android apps (opens in new tab) containing banking trojans.
The researchers at ThreatFabric (opens in new tab) have identified four families of banking trojans that have recently been distributed via Google Play. In a breakdown of the modus operandi, they note that these strains have collectively led to “significant” financial losses for the targeted banks.
The four trojans hid inside all kinds of apps, with the most prominent one named Anatsa, which alone accounted for over 200,000 downloads. The researchers found Anatsa inside apps that posed as QR code scanners (opens in new tab), document scanners (opens in new tab), and cryptocurrency (opens in new tab) apps.
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Difficult to detect
The major takeaway from the analysis is the extent to which the apps went to avoid being flagged.
“A noticeable trend in the new dropper campaigns is that actors are focusing on loaders with a reduced malicious footprint in Google Play, considerably increasing the difficulties in detecting them with automation and machine learning techniques,” note (opens in new tab) the researchers.
Furthermore, according to the analysis, the threat actors only manually activate the installation of the banking trojan on an infected device in case they need to lure more victims in a specific region of the world. This behavior further complicates the discovery of the trojans using automated detection mechanisms.
It's no surprise, then, that the researchers say that almost all of the trojans had a very low score on VirusTotal at some point in time.
"A good rule of thumb is to always check updates and always be very careful before granting accessibility services privileges – which will be requested by the malicious payload, after the "update" installation – and be wary of applications that ask to install additional software," said Dario Durando, mobile malware specialist at ThreatFabric, sharing a strategy with ZDNet (opens in new tab) to help users detect trojanized apps.