Adult social networking site Adult Friend Finder has settled with the US Federal Trade Commission over explicit pop-up ads that were sent to users.

According to the FTC, Adult Friend Finder and its affiliates used both adware and web-based pop-ups to promote the site, which bills itself as "the world’s largest sex & swingers personal community."

The pop-ups contained explicit photos and the FTC said that they were often displayed indiscriminately. In some cases, the commission found that the pop-ups were being served to users who had been searching such as 'flowers' and 'vacation.'

Adult Friend Finder agreed to suspend the offending pop-ups. The company will also be required to prevent any further incidents and will be forced to keep records to ensure that it is complying with the order.

Over the last two years the FTC has been aggressive in pursuing advertisers who make use of unscrupulous affiliates. The most notable case was that of adware vendor Zango, which overhauled its affiliate program after running afoul of the commission in 2006.

Sunbelt Software president Alex Eckelberry predicted in a company blog that Adult Friend Finder could face a formidable challenge in cleaning up its affiliate program. The security firm has already found evidence of spamming by affiliates in the hours after the deal was announced.

"While AFF may no longer provide materials to their affiliates which are sexually explicit, this company will need to pay particular attention to its affiliate channels," wrote Eckelberry.

"There's just too much money there."