AOL blocks Messenger spam

America Online has changed its network to stop pop-up 'spam' reaching its customers, the company announced yesterday.

In a move quickly discovered by spammers, the AOL Time Warner subsidiary made a few technical changes last week to stop a relatively new type of annoying message that uses the Windows messenger service to cause unsolicited marketing to appear on a person's screen.

"In the ongoing fight against spam on a wide-ranging front, this is a big victory for our members," said AOL spokesman Andrew Weinstein.

The technique uses a feature of Windows intended to let network administrators notify their customers of critical maintenance issues such as server downtime or schedule backups. The text-only messages pop up in a dialog box on top of any other window being used at the time. The vulnerability affects Windows 95, 98, NT, 2000 and XP.

Software from companies such as DirectAdvertiser and BroadcastMarketer allow direct marketers to send thousands to hundreds of thousands of such messages every hour to random internet addresses. Each success means a message appears on a PC's desktop. Spammers like the technique because it forces an internet user to see a message and close it.

Response rates are high, said Anish Dhingra, president of Broadcast Marketer. Dhingra claims that the technique isn't spam, because affected users can simply turn off the Windows feature that allows the pop-up messages to appear.

"It is pretty hard to opt out completely from spam," he said. His company noticed that AOL had made the modification when customers started calling in, he said.

Dhingra, whose software can send up to 135,000 messages in an hour, believes the company's software will be able to get past AOL's blockade in a few weeks. "Pretty much our next version will have a workaround for AOL," he said.

That means that America Online may find itself in an arms race. "We've blocked this exploit, and we'll continue to fight spam," AOL's Weinstein said.

Robert Lemos writes for News.com