US regulators have acted against a company that used a Microsoft loophole to bombard PCs with pop-up ads.
The ads appeared on screen even if no one was using the PC
San Diego-based D Squared has been banned from using a little known feature, Windows Messenger, to send unwanted adverts to computer owners.
Ironically, the pop-ups were advertising software which blocked pop-ups.
The company admitted no wrong-doing and received no financial penalties. It claimed it settled to avoid litigation.
The Federal Trade Commission (FTC ) found that the ads violated US consumer protection law.
According to the FTC, the pop-ups sent by D Squared could appear even when a user was not actively web browsing.
It said that they appeared as often as every 10 minutes, causing data loss and, in some cases, computer crashes.
D Squared was created by two college students Anish Dhingra and Jeffrey Davis.
It is alleged that their company tried to sell its technique to others, claiming it could send pop-ups to as many as 135,000 internet addresses each hour.
Lawyers for the pair said that they were not trying to extort consumers by bombarding them with ads and argued they only intended to send one a day to computer users.
Ads were "an annoyance you have to deal with in a free society," lawyer Anthony J. Dain is quoted as saying.
The Messenger service in Windows allows computer network administrators to communicate with each other but is unnecessary for home users.
D Squared has also been banned from sending pop-up ads over the hugely popular instant messenger services, which allow users to communicate in real-time.
It will also have to let the FTC monitor its business activities for the next five years.
The loophole has led Microsoft to take steps to prevent its Messenger service from being used as a conduit for advertisements in future.
Although marketers regard pop-ups as one of the most effective ways of advertising online, many surfers find them hugely annoying.