A security problem with MySpace has the potential to botch up law-enforcement efforts to track bad actors on the social-networking site.

An increasing number of MySpace profiles contain a few lines of code that automatically subscribe people to the profile's video channel, said Chris Boyd, security research manager for FaceTime Communications.

After the visitor has been added, the person running the profile can see the subscribers. For people who don't abuse MySpace, the problem may not appear to be a huge deal, Boyd said.

But hackers often are running dozens of "puppet" MySpace accounts, which are used for a variety of malicious acts such as spamming or trying to vandalize other profiles, not for social networking, Boyd said.

So when a visitor is added, it's a tip-off that someone could be tracking their movements in order to expose them for abusing MySpace, Boyd said.

Hackers "are using every trick in the book they can to know who is watching them," said Boyd, who has posted more details on his blog.

That's particularly bad for law enforcement, which may invest weeks in "digital stakeouts" observing certain profiles as part of pedophilia investigations, Boyd said.

Hackers have been inserting the code on their pages since at least October 2007. MySpace was notified of the problem in late March but has yet to fix it, although Boyd said the company sent him a personal e-mail labeling the problem a "system error."

The code doesn't tell the person running the profile how many times a particular visitor comes to their site or when, Boyd said. But in combination with an IP (Internet protocol) address "tracker," a profile owner could compile a more complete picture of visitors.

MySpace prohibits tools such as IP trackers, which can narrow down to certain geographic areas where visitors are based. Many of the trackers advertised on dodgy forums simply don't work, Boyd said. Nonetheless, hackers keep finding ways to game MySpace.

There are a couple defenses against this latest problem. If you're automatically added to someone's video channel, you can simply unsubscribe and avoid going back to the profile until MySpace has fixed it.

Another defense is adding the URL (Uniform Resource Locator) "vids.myspace.com" to the "hosts" file, an internal PC file that matches domain names with Web sites. The file can be configured to block any domains a user specifies.