Lots of rule modifications in this release as well as some fixes and new rules.
Security Fix - This module pack resolves a potential recursive evaluation DoS condition in SO rules that utilize the built-in content match API function. Sourcefire recommends installing this release as soon as possible if high latency is encountered when dealing with large SMB file transfers.
As a result of ongoing research, the Sourcefire VRT has added multiple rules to the web-activex, specific-threats, web-client and multimedia rule sets to provide coverage for emerging threats from these technologies.
A detailed advisory as well as a complete list of new and modified rules is available at:
http://www.snort.org/vrt/advisories/vrt-rules-2009-01-20.html