Apps similar to mod_httpbl include Bad Behavior, which is free and open source. Other options are AbyssGuard and blq. In total there are three Anti-Spam Tools like mod_httpbl for Mac, Linux, the web and Windows.
Bad Behavior is designed to integrate into your PHP-based Web site, running as early as possible to throw out spam bots before they have the opportunity to vandalize your site with their junk, or even to scrape your pages for e-mail addresses and forms to fill out.
Visitor verification that blocks scrapers, bots, and attacks before they reach your site. Zero false positives. Works with any platform.
Some organizations, such as the MAPS RBL and MAPS DUL, publish lists that identify potential sources of spam and email abuse. The blq utility is a Perl script that queries one or more of these lists to determine if a particular host is listed.
