BBC News Online: Sci/Tech

AOL fixes hole in messaging program

Program has millions of registered users

"The issue was resolved," said AOL spokesman Andrew Weinstein. "It was done on computers at AOL, so users don't have to do anything."

Computer security experts had warned that the program, which allows users to exchange real-time messages and computer files, was vulnerable to hackers.

The security flaw could have allowed someone to seize control of a user's computer and then order it to erase its own data files or send computer viruses to other computers.

"To our knowledge, no users were affected by this issue prior to its resolution," said Mr Weinstein.

Windows messaging at risk

AOL Instant Messenger has over 100 million registered users, but only the Windows version of the software was at risk.

The vulnerability was discovered by the security research team w00w00, a group founded by a 19-year-old American student.

In a statement, w00w00 said "the implications of this vulnerability are huge and leave the door wide open for a worm", a computer virus that can spread by itself, without human intervention.

The flaw was similar to the problem recently found in Microsoft's Windows XP operating system, which would have allowed a hacker to remotely delete files or take over a computer.

Microsoft issued a patch to rectify the problem last month.