The Conference on E-mail and Anti-Spam, held in Mountain View, California this week, brought to light some interesting trends in spam and research on where it comes from. According to a report in today’s MIT Technology Review, new research highlights just how spammers get their email address lists in the first place, and how they relay the messages.

According to a paper coming out of Indiana University that was presented at the conference, it is common for spammers to gather email addresses from Web pages, in much the same way that a search engine’s spider works. When you print your email address on the Web, you’re risking spam–automated spam crawlers, constantly survey the Web, looking for email addresses, and sooner or later, it will get to yours. The research showed that when you include an email address on a comment board on a web site, there is a high probability of receiving spam. But what about when you register on a web site? It’s very common for a web site to require user registration to gain access, and this is a legitimate way for a site to operate–you’re in essence, trading your email address for access to information. But the registration process is less likely to result in spam, especially when more legitimate and mainstream sites are conducting the registration.

Is there a way to stop the spam crawler programs? The researchers say yes, and it should be a straightforward process to block them and thereby protect email addresses submitted to a web site from being harvested.

A common technique seen throughout the Internet is to replace the @ symbol with the word “at”, to foil the automated harvesting mechanism. Surprisingly, this very simple technique has proven to be highly effective.

The Indiana University researchers recommended users exercise caution when divulging email addresses–and also noted that spam can arrive very quickly, in many cases, in less than an hour after entering an email address on a web site. The spamming crawlers tended to be fairly aggressive as well, ranging from visiting two times per minute to over 50 times per minute.