In an attempt to reduce the number of viruses and SPAM emails that we’re getting hit by, I’ve modified our mail system so it will refuse to talk to any machine that fails a Reverse DNS lookup. The majority of mail servers are set up so that a Reverse DNS on their IP address will map to a real name. If this fails, it’s usually a sign that the sending machine is an infected workstation.
By blocking these machines outright, we do not have to receive their infected/junk emails. This should hopefully save us quite a bit of incoming bandwidth, thus reducing our monthly hosting charges. It should also help reduce the amount of SPAM we receive.
I’ve also modified the “Shields” system so that it only blocks sites that have sent 3 or more viruses in the past day or two. It was blocking sites if they’d sent 3 or more viruses in a week. This was much too long and resulted in the blocking of some valid sites that accidentally let a few through.