This is in response to the false positives for audit 163, NULL sessions. Audit 2913 is totally unrelated.
Audit 163 (NULL session connections expose sensitive info via Windows Net??? API calls) and 2091 (limited NULL session exposure through the SRVSVC and/or SAMR named pipes) deal with NULL session vulnerabilities.
Funny that I just spent 11 hours today figuring out why we sometimes report false positives on 2003/XP and greater systems. Unlike 2000, NULL session connections are always allowed on 2003/XP which in conjunction with certain combinations of registry values result in false findings. The audits have been fixed and will be availble in late November or early December.
I will be preparing a KB article tomorrow explaining the quirks in the 2003/XP MS solution to NULL session restrictions and the criteria we now use to report findings. Instructions on how to resolve the issue will also be updated with more detail.
Craig