The following are brief summaries of my technical experience with the Microsoft Windows, Linux and Mac Systems.
Operating Systems – openSUSE, Red Hat, Fedora Core, Ubuntu, Yellow Dog, BackTrack, Helix, and BartPE.
Spam Filter
I built a fully functional Spam Filter system using Amavis, Postfix, SpamAssassin & ClamAV with a combination of various DNSBL’s & RBL’s to check against the IP address and the message content. How it works is when an e-mail comes into the Spam Filter it goes through several checks before sending it off to the exchange server. I’ve programmed the server to use Postfix as the front-end and back-end e-mail relay system. The spam filter has a service listening on port 25 called Postfix. E-mail is recieved on this port and then Postfix runs through a list of manual configurations and automatic configurations. The manual configurations are a set of statically assigned denial or allow sequences. The automatic configuration gets updated from online repositories. Postfix also runs a check on several RBL’s & DNSBL’s to see if that IP address is originating from it’s sender, check’s if the IP address is a known spammer, and looks for SPF records for domain validation.
After the initial Postfix checks are done the message is either rejected or passed through for further processing. If it is rejected the users get’s a notification why it was rejected, if the message seem’s good it will then be passed onto a service called Amavis which sifts through each e-mail message using both services ClamAV for Anti-Virus & SpamAssassin to check for spam markers within the content of the e-mail message.
After all these checks are completed it will then either reject the e-mail message or send it back to Postfix to be relayed to the Exchange Server. At the Amavis level if an e-mail is rejected I do also include a message why it was rejected. Spam filtering isn’t perfect there is always a chance for a false positive, in the event this happens we can determine by the rejection notice how to fix that particular e-mail message.
I included a flow chart of what an e-mail message goes through below.
[More Coming Soon]
