Microsoft is scrambling to update its Windows Media software after a hacker released a programme that circumvents a safeguard designed to prevent people from freely copying digital movies and songs.

Microsoft is attempting to plug a glaring hole in some versions of its Windows software, a weakness similar to those exploited by the devastating “Blaster” and “Sasser” attacks, a security expert says.

Traffic on the many parts of the Internet slowed dramatically early today, the apparent effects of a fast-spreading virus-like infection interfering with Web browsing and delivery of e-mail.