I run a small network of computers approximately 15 machines big. My ISP is now telling me that we have an open proxy and I'm relaying spam. Is there a systematic way to go through and check for this? I'm completely bamboozled and my ISP isn't offering any suggestions to help fix. Do I start at each individual computer and run some scans or can I efficiently monitor for someone exploiting this port. We have a hardware firewall FVL328 from Netgear.