Trojan downloader named Renos that installs rogue security software was the most prevalent threat in the second half of 2008, increasing by 66 percent. Malware Protection Center found that these threats accounted for more than half of all of the malware removed by its Malicious Software Removal Tool from July through December of last year. Only about 41 percent of browser-based exploits on pre-Vista versions of Windows targeted Microsoft products, that number drops to about five percent on Vista. That s a trend that bears watching.
Source: https://threatpost.com/microsoft-rogue-security-software-fastest-growing-online-threat-040809/72530/