How to Prevent Outgoing Spam on Your Server

Often when we think of spam, it usually relates to incoming spam inundating mail servers and bogging down systems. Another way spam can harm your dedicated server is from the inside.

Many spammers do not setup their own servers or paid hosting accounts to send spam. They want to be anonymous. Therefore, they often use other people’s servers, possibly even yours, to send their spam. They may have signed up for your hosting service using false credentials, or they might even find an exploit in your mail server or other area of your system that allows them to use it to send spam. In either case, it takes a serious toll on system resources.

To prevent people from using your server to spam, you can take some basic precautions:

  • Disable the MTA. If you do not use your server for mail, you do not need Sendmail, Postfix, or any other mail server running. Disable it completely.
  • Lock down /tmp. Many exploit scripts will deposit spam or IRC bots in /tmp and send out nightly unwelcome gifts to random people.
  • Enforce strong passwords – Protecting user accounts will give spammers fewer options
  • Monitor and scan – Monitor your server for suspicious activity and do regular scans for malware

With a few simple precautions you can all but eliminate the chance that anyone will be able to use your server to send spam.

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