Is there any free software out there that can help locate a Spammer within our network? We know that they are not using our mail server. We suspect it is someone with a virus on their machine however, our antivirus for whatever reason can not find them. I beliveve the reason why our antivirus does not find them is because I think the culprit is in a seperate VLAN. This only narrows it down to about 100 machines. I wish to narrow it down further but economic times being what they are I was looking for a free software solution if possible. We have already tried turning off port 25 but were unable to locate the spammer. Please help.