Java exploits predominate, including some still successfully targeting bugs from 2008.



From InformationWeek:

One in 20 PCs is infected with malware, according to statistics gathered by a free Microsoft scanning tool. Interestingly, the average infected PC contained 3.5 pieces of malware, and most of those malware applications exploited Java vulnerabilities.
Those findings come via Microsoft Safety Scanner (MSS), a free, recently updated tool from Microsoft that's designed to clean up after a malware infection. The tool expires 10 days after being downloaded to force users to download a new version with the latest updates.

  Microsoft Finds 5% Of PCs Running Malware