“The apps were 'Trojanized,' for a better word,” said Tom Parsons, a senior manager with Symantec's security response team. “With the phones being 'rooted,' the attacks can do almost anything, including pulling data off the phone,” he said, referring to the malware's ability to gain root access to the devices.
The apps were available for about four days on the Android Market, Google's official app store. According to San Francisco-based smartphone security firm Lookout , between 50,000 and 200,000 copies of the apps were downloaded by users.
All the apps were infected with the same malicious code, said Kevin Mahaffey, the CTO of Lookout, and came from three different publishers. The malware, dubbed “DreamDroid,” lets attackers compromise Android smartphones, then connect them to a command-and-control server (C&C) which can issue orders to the devices.
In some cases, the malicious apps were pirated versions of legitimate Android software.
Mahaffey called the appearance of so many infected apps on the official Android Market a turning point in mobile malware. “This was a tier 1 market that had a significant number of malicious apps that were downloaded a significant number of times,” he said.
Previously, malware-infected Android apps, like the bogus “Steamy Window” app that Symantec discovered Monday, were posted on third-party download sites, not Google's own e-mart.
Mahaffey confirmed that Google has yanked the 50-some apps from the Android Market, but said that as of late last night, the mobile OS maker had not pulled those apps from users' phones.
Like other mobile app distributors, such as Apple, Google has the ability to flip a switch that remotely removes questionable or malicious apps from all Android smartphones. Google has pulled the uninstall switch at least once before, in June 2010.
“Google's very responsible with that power,” said Mahaffey, explaining why the apps have been pulled from the Android Market but not yet removed from users' phones. “They want to make sure that it's used only in cases when they're sure they're removing only malware.”
Google declined to comment on what actions it has taken so far to protect users.
Mahaffey said Lookout is still analyzing the malware, its capabilities and how the attackers hoped to profit from the compromised smartphones, but said his company's initial investigation had uncovered a C&C server located in Fremont, Calif.
The infected phones are communicating with the server and sending information — including the user-specific subscriber identifier, also known as the IMSI (International Mobile Subscriber Identity), and the phone's SIM card's serial number — via an encrypted channel. The C&C server seems to be hosted on a legitimate system that hackers had breached previously.
Parsons and Mahaffey differed when asked how the incident reflected on Google and the security of its Android Market.
“More than anything, it shows how popular Android is,” said Parsons. “Google has a major challenge vetting nearly a thousand new apps each day, and this may indicate that that vetting isn't robust enough.”
But Mahaffey saw a silver lining in the cloud.
“I'd argue that it speaks to the openness of the Android platform that a user was empowered [enough] to notice [a malicious app],” Mahaffey argued, referring to reports that an Android smartphone owner was the first to go public with his suspicions. “We will see more people be more vigilant.”
Both Parsons and Mahaffey applauded Google for quickly responding — within minutes of the first reports — to the situation by deleting the apps in question from its marketplace.
“After this, there will increased vigilance by a lot of people,” said Mahaffey, hinting at Google's likely wake-up call. “For users, the best advice is to pay attention to what you download.”