Spam filters: Making them work
- — 23 September, 2008 09:10
5. Choose blacklists and reputation lists wisely. Jennings points out that many spam filters let the customer choose which blacklist, if any, to use. If your organization relies on a blacklist to stop spam, he recommends that you check the management policies of the lists. Briggs notes that some are driven purely by user complaints, so relying on them will invariably lead to false positives.
6. Make sure you're not a spammer. If spam goes out from your systems, even unintentionally, it can hurt your reputation and increase the likelihood that you'll end up on spam blacklists. If your e-mail address appears in the "from" line of enough spam, Jennings says, your reputation may suffer to the point that you will have trouble sending legitimate e-mail.
A three-pronged approach will help keep your reputation intact:
- Curb your users' questionable Web browsing, suggests Stephen Pao, vice president of product management at security vendor Barracuda Networks . If users visit dangerous or objectionable sites, malware from those sites could be installed on their computers, which could then be used to send spam.
- Stay up to date with security patches and virus and malware definitions to ensure that spammers can't take over your systems and use them to send spam, Pao says.
- Use outbound filtering to make absolutely sure no spam is being sent from your systems, Jennings suggests.
7. Check your own spam reputation. If your organization is on a blacklist, your recipients might not receive your outgoing e-mail. Lochart recommends regularly checking your own reputation by visiting sites such as Habeas.com, which provides companies with a free reputation check and helps them manage their online reputations.
If you find your company unjustifiably on such a list, Lochart suggests that you contact its administrator to voice your concerns. But getting "un-blacklisted" can be difficult.
8. Warn users to be wary of red-flag words. In sending e-mail, avoid words that are associated with spam, says Lucio Gonzalez, a systems specialist and e-mail administrator at South Texas College in McAllen, Texas. These include hey , hello , free , enlarge , pharmacy , alert and diploma.
Conversely, try to include recipient-specific information in your messages, such as project names or personal references unique to your recipient. Doing so can lessen the chance that Bayesian analysis of your message will cause it to be flagged.
By reducing false positives, you help ensure that real e-mail from your senders actually gets to you and that real e-mail from you actually gets to them.