My ISP is complaining that malicious (viral) traffic is coming from our IP address against other ISP clients, on port 139 and 445. I have since obtained a much better router, through which I can lock down this traffic from leaving the network. However, that being a great solution for the Internet, it is a band-aid solution as far as the source of the infection is concerned. I probably won't have a problem dealing with the malware, but I need to find it, and it's a large network - well, it's only 30 computers spread over a large area, but it's still a needle in a haystack. My ISP has sophisticated equipment to detect this stuff, but does anyone know of any reasonably priced or free tools with which I can scan and detect such traffic or something serving this stuff on my LAN, without having to go to each and every PC? This is something I should probably deal with quickly, so it is fairly urgent - thanks.