Craigslist will require anyone posting ads to the Web's site's "erotic services" section to submit a working phone number and credit card, the online classified publication said Thursday.
The new measures are the result of negotiations between Craigslist and 40 state attorneys general and are designed to thwart ads for prostitution and other illegal activities.
San Francisco-based Craigslist has long implemented electronic safeguards to prevent this kind of advertising, but an entire cottage industry has sprung up around selling software and other services that help circumvent the blocks, the company said in a statement.
"These businesses facilitate the placement of ads for illegal services that would otherwise be blocked by Craigslist's protective measures," Craigslist said in the statement.
Craigslist has also agreed to sue 14 of the companies accused of helping illegal advertisers to evade the site's defenses, the company said. The Web's largest classified section is also sending "cease and desist" letters to numerous other companies offering such services.
In March, Connecticut Attorney General Richard Blumenthal sent Craigslist's management a letter accusing the site of allowing users to post ads for prostitution in violation of its own terms of service. The company says, however, that it has a long history of cooperating with law enforcement and doing everything it can to prevent crime on the site.