Google has removed nearly two dozen malware-infected apps from its official Android Market in the last several days, a security company said Sunday.
So far this year, Google has yanked more than 100 malicious Android apps from its download distribution channel.
San Francisco-based Lookout Security said that it and other vendors had notified Google of several recent waves of malicious apps - 22 apps altogether - that reached the Android Market. Google has yanked those programs from the e-mart, said Lookout.
Lookout spotted nine malware-infected apps last week, and another 13 over the weekend.
The company dubbed the malware bundled with the fake apps "RuFraud," and said that the code sent spurious text messages to premium numbers, racking up revenues for the criminals.
Users in the UK, France, Germany, Italy, Poland, Russia and several other eastern European and central Asian countries were targeted, while North American users were not affected, since RuFraud was written not to target the US.
As in previous malicious app campaigns, the RuFraud apps borrowed elements of legitimate apps, but did not simply snatch complete apps, then re-package them with malicious code, said Lookout.
"They borrowed aspects of other apps, including terminology and in some cases identical text," said Tim Wyatt, a principal engineer at Lookout.
Fake games, horoscopes and wallpapers
The recent RuFraud operations began with horoscope apps, said Lookout, then moved on to Android phone wallpapers - including one for the Twilight series of movies - and downloaders posing as accessories to bestselling games such as "Angry Birds" and "Cut the Rope," then finished with a round of fake games, Lookout's researchers said.
That last run accounted for the majority of downloads before Google pulled the apps. Lookout estimated that about 14,000 copies of the fake games were grabbed by users.
"A couple of instances of the apps from this weekend really drove that [number]," added Derek Halliday, a Lookout senior security product manager. "The others really didn't affect very many people as far as we know."
Google has had trouble keeping malware out of the Android Market.
In July 2011, Lookout found four apps there that were infected with a variant of the "DroidDream Light" malware. The July discovery was the third instance of DroidDream-infected applications making it into Google's estore, following an initial campaign in March and a second in early June. Those two waves forced Google to pull more than 80 poisoned apps from its store.
Lookout uses its own malware detection technology to uncover malicious mobile apps. According to Halliday, Lookout detects rogue apps "as soon as they're published."
Google too relaxed on scanning apps
"Google is very responsive," said Wyatt, referring to the Android maker's moves when it's told that tainted apps are in its marketplace. "From notification to pulling the apps is generally on the order of minutes," Wyatt added.
Security experts have regularly knocked Google for not proactively scanning apps submitted to the Android Market and repeated that criticism today.
"We have already stated several times that the requirements for becoming an Android developer that can publish apps to the Android market are far too relaxed," said Vanja Svajcer, a principal virus researcher with UK-based antivirus vendor Sophos, in a Monday blog . "The attacks on Android Market will continue as long as the developer requirements stay too relaxed."
Svajcer identified some of the fake games that the attackers used to spread RuFraud, a list that included "Angry Birds," "Assassin's Creed Revelations," "Cut the Rope" and "Need for Speed."
Unlike Google, other app store operators vet submissions and scan apps for possible malware. Microsoft, for example, has promised to review apps submitted to its PC- and tablet-oriented Windows Store for security issues; Microsoft's market is slated for opening in late February alongside the release of the first Windows 8 public beta.
When asked if Lookout had offered Google the former's technology for scanning apps submitted to the Android Market, Halliday declined to comment.