Android users in more than 20 countries have been infected with a particularly aggressive malware program that bombards devices with unwanted advertisements.
Researchers from FireEye found that the malicious component, nicknamed Kemoge, has been seeded inside what appear to be legitimate apps offered on third-party application stores.
"This is another malicious adware family, possibly written by Chinese developers or controlled by Chinese hackers, spreading on a global scale that represents a significant threat," wrote Yulong Zhang, a staff research scientist with FireEye.
Whomever created Kemoge repackaged legitimate apps with the malware and then promoted them on websites and through in-app ads to persuade people to download them.
Zhang listed a dozed affected apps: Sex Cademy, Assistive Touch, Calculator, Kiss Browser, Smart Touch, Shareit, Privacy Lock, Easy Locker, 2048kg, Talking Tom 3, WiFi Enhancer and Light Browser.
Third-party apps stores are considered risky places to download Android apps, as hackers frequently upload malicious apps to them. Google performs a security check on apps in its Play store, although harmful ones occasionally sneak in.
Kemoge not only displays unwanted ads, but it's also loaded with eight root exploits that target a wide range of Android devices, Zhang wrote. A successful attack using those exploits means an attacker would have complete control over the device.
Kemoge will collect a device's IMEI (International Mobile Station Equipment Identity) and IMSI (International Mobile Subscriber Identity) numbers, information on storage and apps, and send the information to a remote server.
That command-and-control server was still running, Zhang wrote. An analysis of traffic exchanged between an infected device and the server showed Kemoge also tries to uninstall antivirus apps.
Curiously, FireEye came across an app called Shareit in Google's Play store that was signed by the same digital certificate as the malicious one found on the third-party source.
The Google Play version of ShareIt did not have the eight root exploits or contact the command-and-control server, but it did have some of the same Kemoge code libraries. It now appears to be gone from Google Play.
"We have notified Google about this threat," Zhang wrote.