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Computerworld - For the second time in three months, Google yanked dozens of malware-infected smartphone apps from the Android Market.

The 34 apps were pulled over the weekend and Tuesday by Google after security researchers notified the company.

Google acknowledged giving some Android apps the heave-ho. "We've suspended a number of suspicious applications from Android Market and are continuing to investigate them," a Google spokeswoman said in an email reply to questions late Tuesday.

As in the March episode, when Google removed more than 50 apps, the newest round consisted of pirated legitimate programs that had been modified with malicious code and then re-released to the Android Market under false names.

But there was an important difference to this campaign, said Kevin Mahaffey, co-founder and CTO of Lookout, a San Francisco firm that specializes in mobile security.

"These apps have the ability to fire up a page on the Android Market," said Mahaffey, adding that the hackers can send commands to the smartphone telling it which Market page to display.

He speculated that the attackers probably intended the new feature as a way to dupe users into downloading additional rogue apps that would have malicious functions, just as a hijacked PC is told to retrieve more malware. "They seem to have been designed to encourage people to install additional payloads," Mahaffey said.

Mahaffey said it was impossible to deduce hacker intent from the malicious apps' code, but he believed the criminals took the new path because social engineered attacks -- those that rely on tricking victims into installing malware rather than depending on an exploited vulnerability -- are more difficult to defend.

"Social engineered attacks are much more subtle, but very powerful because they're hard to protect against," said Mahaffey. "It could be they changed because either [the attackers] believed exploits were a dead giveaway, or they found this more effective."

Lookout and AVG Technologies of the Czech Republic uncovered malicious apps on the Android Market and reported their findings to Google. According to Mahaffey, Google pulled the apps "almost instantaneously."

It's unclear how the attackers planned to turn a profit on the new campaign of rogue apps.

"They could do things like listen in to all the banking transactions [conducted using the smartphone]," said Omri Sigelman, the vice president of products at AVG Mobilation, AVG's mobile security arm, in an interview Tuesday.

Both Mahaffey and Sigelman said that the same group responsible for the March malware was behind the most recent attempt to infiltrate Android phones.

The new rogue apps contained what Mahaffey called "Droid Dream Light," a stripped-down version of the DroidDream code used to infect apps in March.