An Email Filtering Script

Last year, the SoBig virus humbled me. My team uses Microsoft Exchange Server to manage our internal email system and host several closed external discussion lists. We use client-side spam software to filter out noise from our Inboxes, but we had nothing in place to filter email on the server.

After SoBig hit, each member of my team manually filtered roughly 1GB of email a day. Most of the volume was due to the virus and the inevitable virus-alert messages that found their way to our server. Our server not only had to process each offensive email message but also had to devote disk space to storing it and network bandwidth to transferring it to the user's Microsoft Outlook Inbox. Then, the user's Outlook filters took time and consumed resources to delete the message from the Inbox and notify the server to delete the message from the user's Exchange mailbox store. To mitigate the problems, we decided to write a Perl script to run on our Exchange server and filter out on arrival all incoming email that might be a virus. . . .