Google recently removed 145 applications from Google Play after they were found to carry malicious Windows executables inside, Palo Alto Networks reveals.
Most of the infected applications, Palo Alto's researchers say, were uploaded to the application store between October and November 2017 and remained there for over half a year. Google removed all of them after being alerted on the issue.
While not representing a threat to the Android users who downloaded and installed them, the malicious code within these APKs is proof of the dangers posed by supply chain attacks: the software developers built these applications on compromised Windows systems.
Some of the infected Android applications had over 1000 downloads and 4-star ratings before being removed from Google Play.
The security researchers discovered that some of the infected APKs contained multiple malicious PE files at different locations, with different names. However, two malicious files were found embedded in most applications.
One of the files was present in 142 APKs, while the second had infected 21 APKs. The security firm also found 15 apps with both PE files inside, as well as some APKs with a number of other malicious PE files inside.
The researchers also note that one malicious PE file that infected most of the Android apps was a keylogger. The malicious program attempted to log keystrokes, including sensitive information like credit card numbers, social security numbers and passwords.
To appear legitimate, these files use fake names, including Android.exe, my music.exe, COPY_DOKKEP.exe, js.exe, gallery.exe, images.exe, msn.exe and css.exe.
When executed on Windows systems, the malicious PE files would create executable and hidden files in Windows system folders, including copies of themselves, would change Windows registry to auto-start after system restart, would attempt to sleep for long periods of time, and also showed suspicious network connection activities to IP address 87.98.185.184 via port 8829.
“Interestingly, we saw a mixture of infected and non-infected apps from the same developers. We believe the reason might be that developers used different development environment for different apps,” Palo Alto Networks says.
The malicious PE files cannot directly run on Android devices, but, if the APK is unpacked on a Windows machine and malicious code executed, the system becomes infected. As Palo Alto Networks points out, the situation could become much worse if the developers are infected with malicious files that can run on Android.
“The development environment is a critical part of the software development life cycle. We should always try to secure it first. Otherwise other security countermeasures could just be attempts in vain,” the security firm concludes.
Related: Apps Containing Malicious IFrames Found on Google Play