This marks the first time Google has used its kill switch to address actual malicious software in the Android Market. The only previous time the company has utilized the capability was to remove some proof-of-concept malware created by a security researcher.
Revelations about the presence of the malicious apps in the Android Market reached Google's security engineers on Tuesday. The company says that devices running Android 2.2.2 or higher were not affected.
"For affected devices, we believe that the only information the attacker(s) were able to gather was device-specific (IMEI/IMSI, unique codes which are used to identify mobile devices, and the version of Android running on your device)," wrote Android security lead Rich Cannings in a blog post. "But given the nature of the exploits, the attacker(s) could access other data, which is why we’ve taken a number of steps to protect those who downloaded a malicious application."
Given that the malware was designed to download additional malicious software, it's not immediately clear whether affected devices lost sensitive information as a result of this secondary malware.
The malware involved has been designated DroidDream, RootCager, and myournet by various security researchers. According to Jon Larimer, a security researcher with IBM ISS, the malicious code utilizes two known vulnerabilities: the udev exploit (CVE-2009-1185) and an adb resource exhaustion bug, referred to as rageagainstthecage or CVE-2010-EASY. The age of these flaws has caused some to question why Google and hardware makers have neglected to update older Android phones with the latest, most secure operating system software.
Larimer advises resetting affected phones to their factory state. "With root access it's possible to install components that aren't visible from the phone's user interface and can't be easily removed," he wrote. "For this reason, any compromised phone should be reset to it's factory default state -- in some cases this may require a trip back to the phone store."
Symantec estimates that between 50,000 to 200,000 people downloaded one or more of the 52 malicious apps during the four days they were available.
In addition to removing an undisclosed number of applications from the Android Market, Google suspended the associated developer accounts and contacted law enforcement officials. Whether there are any legal consequences for the creators of the malware will depend on the extent of cybercrime enforcement in the countries where the individuals responsible are located.
Google is distributing a specific piece of security software to affected users, the Android Market Security Tool. The company is notifying users who receive the software; it's not necessary for those who didn't download any of the malicious apps.
Cannings says that Google is working on a number of additional security measures to make Android Market more secure and is working with partners to improve software security. The company declined to elaborate on whether the steps it is taking involve additional human oversight or whether they're exclusively technical.