The latest statistics come on the heels of Microsoft's recently published Security Intelligence Report, which found worms jumped 98.4 percent to the number two threat, behind Trojans. Trojans include rogue antivirus software.
One of the worm families Microsoft attributed that jump to was TaterF, which so far is also the most prevalent piece of malware MSRT has killed this month, according to Microsoft's latest statistics: The TaterF worm was found on 239,870 machines. TaterF is a worm that steals online gaming credentials and spreads via Microsoft's Autorun feature and has hit enterprises hard because users who play games at home infect their work machines via USB keys, for instance, according to Microsoft.
According to the SIR report from earlier this month, the number of machines infected with TaterF has increased from 2 million machines in the second half of last year to 4.9 million in the first half of this year.
This month, the top threats found by Microsoft's MSRT are mainly password-stealers like TaterF that grab online gaming credentials, online banking credentials, and other online user accounts. Rogue AV products and Trojan downloaders for them were also high on the list, as well as Trojan downloaders that typically infect machines via drive-by attacks.
Koobface remains in Microsoft's top 25 malware list, but is no longer in the top 10. It's now No. 14 on the list, found in 36,300 machines. "Online Social Network sites such as Facebook continues to boost their security hardening to protect their customers and we welcome their actions," blogged Scott Wu, a member of the Microsoft Malware Protection Center.
Other top malware threats this month so far are the Alureon family of Trojans that steal data and modify DNS settings (141,358 machines), the Bancos family of Trojans that steal passwords and online banking credentials (138,803), and the Renos family of Trojan dowloaders for rogue AV (115,970 machines).
The MSRT also found 78,161 machines infected with the Cutwail spam bot, a family of Trojan downloaders.
Microsoft this month added two new rogue AV families to the list of malware its tool detects -- Win32/FakeVimes and Win32/PrivacyCenter. And so far, Microsoft has cleaned up more than 110,000 machines infected with those two rogue programs.
Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message.