Japanese peripheral vendor IO Data has accidentally added a Windows worm on some of its external hard drives, the company has warned.

Hard drives in the HDP family were infected with the Tompai-A worm. After infecting a system, the worm connects to the internet and awaits further commands from its creator. The system is effectively turned into a zombie computer and can be used to commit identity theft.

The worm is an older threat and most anti-virus applications are expected to be able to detect and remove the worm before it can cause any damage.

The infected hard drives are available on the Japanese market only. The vendor won't supply users with a tool to remove the malware, but instead is advising customers to use their own security application or a 30-day free trial version. Alternatively users can exchange the unit free of charge.

The external UDP hard drives sell at $96 for a 40Gb model and $159 for the 80Gb version. The drives feature a protective mounting padded with silicon gel, which the manufacturer claims will protect against data loss when the drive is dropped.

The affected models and serial numbers are: