According to trend research conducted by security software vendor McAfee, spammers have increased the number of disposable domains that they use and are cycling through new domains faster than in the past. While this trend is certainly a boon for domain name registrars it is in fact a bain for recipients of email as well as mail system administrators.

McAfee said that according to their data major spam campaigns are using 72 percent more domains per hour on average than one month ago. Spammers are apparently trying to outwit URL blacklist filtering systems by stepping up the pace by which such filtering systems must become updated.

"It's a cat and mouse game where spammers try to change their URLs faster than the anti-spam companies can react," said Guy Roberts, development manager at McAfee, Inc. "If it takes traditional blacklists fifteen to twenty minutes to block a site, then that's how fast the spammers need to change their URLs. Since domains cost only $6 per registration, the spammer is spending less than $100 for four hours of advertising."

Manually updated URL blacklists, such as those managed in-house by individual enterprises, might fall behind the changing trends, however realtime filtering services are experiencing increasing usage. McAfee said that it's free SiteAdvisor service is now experiencing more than 100 million unique queries each day. The tool, which is available as an extension for Firefox and Internet Explorer Web browsers, queries McAfee's online SiteAdvisor database to determine whether a given Web site (based on its URL) is safe to interact with. The tool then displays a color-coded icon depending on the rating of the site in question. More information about the service is available in SiteAdvisor's FAQ.

While SiteAdvisor addresses potentially dangerous Web sites comment spam is an ever growing problem for Web sites that allow people to post public comments. At least one new comment spam filtering system, Akismet, was launched to address this particular need. The service, developed by the people behind the hugely popular Wordpress blogging software, works by pre-screening comments before they are posted to a Web site. Akismet relies on a plugin to screen comments. Web site developers can also use Akismet's API to develop their own specialized comment screening code. According to statistics published by Akismet 92 percent of the comments it screens are spam. The service has screened just over 195,000,000 comments as of September 14, 2006 and screens well over 1,000,000 comments each day.