Sony is to stop including anti-piracy software on its CDs after internet security specialists found that it could leave PCs vulnerable to hackers and anti-virus companies classified the program as malicious software. Microsoft also said it would include tools to remove the program in the next update of its anti-spyware application.

The content protection program, which limits the number of times a CD can be copied, installs itself on any Windows PC used to play the CD. Once installed it hides itself, and any other program with a similar filename, from the computer’s anti-virus software. Apple computers and conventional CD players are unaffected.

Last week anti-virus companies discovered a piece of malicious software that mimics the Sony program’s filename and is therefore invisible on any computer that has run a copy-protected CD.

Sony said its decision to stop making copy-protected CDs was a "precautionary measure" and denied that the anti-piracy program presented a security risk. The company issued a statement saying that it would "re-examine all aspects of our content protection initiative to be sure that it continues to meet our goals of security and ease of consumer use."

Sony had previously stood by its technology despite criticism from users of internet forums, who described the technology as heavy-handed. In response, the company created a tool that would allow users to uninstall the protection software. Removing the software eliminates the security risk but also prevents the computer from playing protected CDs.

Attempting to remove the software manually could disable the computer’s CD drive, computer specialists said.

Several anti-virus companies have now put Sony’s program on their blacklist of files that will be detected and removed from user’s computers. In most cases, the part of the program that prevents multiple copying will remain in place, but the part that hides files will be disabled.

"In taking aim at the music pirates, Sony succeeded only in shooting itself in the foot," said Graham Cluley, senior technology consultant at the anti-virus company Sophos. "What they did was not intentionally malicious. If anything, it was slightly inept."

Music companies have been trying to find a way of controlling piracy, which has increased dramatically with the introduction of digital music. Record labels were initially reluctant to make music available over the internet at all, but their hesitation created the demand for file-sharing applications. As a result, illegally copied music became widely available on the internet, free of charge.

Apple’s decision to launch the iPod and its accompanying online music store iTunes created a legal download market, which has been wooing listeners back from illegal sources. High-street retailers such as HMV and Virgin have followed suit, introducing paid-for music downloads, but record labels still lose large amounts of money to piracy.

Sony is among the record companies that have been suing file-sharers in an attempt to deter copyright abuse, but now the company’s anti-piracy policy has landed it in legal trouble of its own. It is being sued in the US by a user who claims that the copyright-protection software on its CDs violated federal laws against malicious software and computer tampering.

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