Defensio 2.0 checks all posts to Facebook in real time against Websense's ThreatSeeker Network, a database of problem URLs, before deciding whether to categorise a post as malicious or unwanted.
This also draws from data gathered by US ISP Radialpoint and URL shortening service bit.ly before performing further heuristic analysis as a final check.
If a bad post is detected, the system logs and informs the user who makes the final decision. As with the original Defensio system - acquired a year ago when Websense bought the company of the same name - it can also monitor web pages for rogue posting, pre-emptively blocking those it deems unwanted.
"We are seeing real threats to Facebook such as Koobface," said Websense senior research manager, Carl Leonard.
According to Leonard, an advantage of Web 2.0 monitoring was that it gave security companies a way of following criminals inside the otherwise closed world of social media, something that many security vendors can't yet do. "We can have visibility into threats on these social networks, and have a fantastic feed of information that can benefit all our customers," he said.
Leonard was not able to say when or if the monitoring might be available other social media sites or feeds such as Twitter, where rogue behaviour can be difficult to spot.
The service is free for anyone with fewer than 50,000 posts per month, and for companies with 15 employees of less. For professional sites or sites with larger volumes of posts, the service starts at $5 (£3) per month, per site.
The issue of abuse of blog and forums by malware hawkers is long established and the company's own research indicates that it's become a big enough issue to drown most unprotected sites with posting spam.
Defensio monitoring has also been integrated with the company's Web Security Gateway system.