You can blame adware for most of the new malicious software, according to a report by Panda Security.
CNET News reports that the third-quarter report from the security company shows that one-third of all malware infections come from adware. Fake virus scanners appear to be the most troublesome, according to this press release, as they prompt users to remove malware that never really existed.
The report also shows that Trojan horses made up 60 percent of all malware during the sample period. Worms accounted for 4.53 percent, while spyware contributed only 2.93 percent.
You can download the full report here.