Here is a list of vendors offering antivirus for Office communications Server 2007:
Well, in fact i have spent some time on this, and i didn’t find anyone yet offering this solution.
There is a Antigen product called Antigen for Instant Messaging, but there is only support for LCS 2003 & 2005. Microsoft i currently branding Antigen for IM to match the Forefront product family but does not yet support OCS, but there should be plans for a release sometime in 2009. The new product will be called Microsoft Forefront Security for Office Communications Server, but we will have to wait
Trend Micro also have products for the LCS versions, and i´m waiting for them to get back to me about when they will support OCS (i’ll update later)
Symantec is the same story, only support for old versions.
Trend Micro reports back that there will be support for OCS 2007 in there “Instant Messaging Security” product, that will be released in Q3 2008.
Update (July 2008):