Malware designed to target devices running Google's Android operating system have surged by 37 percent, says McAfee.

According to the security firm's Threat Report for Q3 of 2011, 60 percent of new samples of malware found last quarter were aimed at Android devices but this quarter saw this rise to 97 percent.

McAfee said one of the most popular forms of Android malware discovered this quarter was SMS-sending Trojans that collect personal information and steal money while malware that records phone conversations and forwards them to the attacker was also popular

At the end of 2010, McAfee Labs predicted that malware would reach the 70 million unique samples by the end of 2011. However, McAfee Labs has now increased this prediction to 75 million unique malware samples to be identified by the year's end.

The security firm said samples of fake Anti-Virus (AV), AutoRun and password-stealing Trojans have surged this quarter after dropping earlier in the year. However, the number of "bad sites" of websites that host malware or have been designed for phishing has dropped, from an average of 7,300 new bad sites in Q2 to 6,500 new bad sites in Q3.

"This has been a very steady quarter in terms of threats, as both general and mobile malware are more prevalent than ever," said Vincent Weafer, senior vice president of McAfee Labs.

"So far this year, we've seen many interesting yet challenging trends that are affecting the threat landscape, including heightened levels of sophistication and high-profile hacktivist attacks."