McAfee (http://www.mcafee.com) has released the "McAfee Threats Report: Second Quarter 2011," showing that the amount of malware targeted at Android devices jumped 76% since last quarter, to become the most attacked mobile operating system.

2011 has also resulted in the busiest ever first half-year in malware history, including a first-ever appearance of Mac fake AV and a significant uptick in rootkits, suggesting that McAfee’s comprehensive malware “zoo” collection will reach a record 75 million samples by the year’s end.

“This year we’ve seen record-breaking numbers of malware, especially on mobile devices, where the uptick is in direct correlation to popularity,” says Vincent Weafer, senior vice president of McAfee Labs. “Overall attacks are becoming more stealth and more sophisticated, suggesting that we could see attacks that remain unnoticed for longer periods of time. High-profile hacktivist groups have also changed the landscape by drawing a line between attacks for personal gain and attacks meant to send a message.”

With an approximate 12 million unique samples for the first half of 2011, a 22% increase over 2010, this has been the busiest first half-year in malware history. With the addition of Q2’s numbers, the grand total of total malware samples in McAfee’s database has reached approximately 65 million, and McAfee researchers estimate that this “Malware Zoo” will reach at least 75 million samples by the year’s end.

In the second quarter of 2011, Android OS-based malware surpassed Symbian OS for the most popular target for mobile malware developers. While Symbian OS and Java ME remain the most targeted to date, the rapid rise in Android malware in Q2 indicates that the platform could become an increasing target for cybercriminals -- affecting everything from calendar apps, to comedy apps to SMS messages to a fake Angry Birds updates, says McAfree.

There are more Mac users than ever before, and as organizations increasingly adopt Macs for business use, Apple now has become more a target for malware authors. Though historically the Apple platform has been unaffected by fake anti-virus (fake AV) software, activity in Q2 indicates that it's now being affected., according to McAfree. Although this type of fake AV is the first of its kind, McAfee Labs does expect fake AV, in general, will drop off over time.

Another malware category that is demonstrating recent steady growth is stealth malware. The tactic of hiding malware in a rootkit is used by cybercriminals to make malware stealthier and more persistent, and has seen this type of attack gain in prominence over the past year, with high-profile attacks such as Stuxnet. Stealth malware has increased more rapidly in the last six months than in any previous period, up almost 38% over 2010.