Computer maker Dell has admitted that some replacement motherboards installed in four of its server lines were infected with malicious software.
But, the firm said, the error had affected less than 1% of motherboards replaced in the past year and no customers had reported that their servers had been compromised.
The error occurred because the motherboards, infected by the W32.Spybot worm, had not been tested as rigorously as those used when the servers were first made, Dell said.
Such cases of pre-infected hardware are rare, but the Dell case comes amid growing concern among US government officials about the security of foreign-produced parts in the supply chain for defence and critical private industries, according to the Financial Times.
Dell discovered the W32.Spybot malware during a quality audit. It has been in circulation since 2003 and is designed to give hackers remote control of machines.
The company said it has put in place 16 additional process steps to ensure that this type of error cannot happen again.