I have rewritten this post now that there are more solutions available on the market. See links below:
Microsoft ForeFront for SharePoint (with SP1)
http://www.microsoft.com/technet/prodtechnol/eval/fssp/default.mspx
TrendMicro PortalProtect
http://us.trendmicro.com/us/products/enterprise/portalprotect/
Symantec Protection 5.1 for SharePoint Servers
http://www.symantec.com/business/products/overview.jsp?pcid=2241&pvid=829_1
McAfee PortalShield for Microsoft SharePoint
It does not list SharePoint 2007 under the system requirements on their site but it does in the datasheet PDF so who knows…
http://mcafee.com/us/enterprise/products/email_web_security/portalshield_microsoft_sharepoint.html
Jeff
