Three London hospitals whose computer systems were infected with a relatively old worm are now almost back online.
Around 5,000 PCs at St Bartholomew's, the Royal London Hospital and The London Chest Hospital were hit in mid-November by an infection of Mytob, a worm that emails itself to other PCs and can be used to put other malicious software on a machine.
About 97 percent of those PCs are now clear of Mytob, according to a statement issued Friday. The remaining PCs, which are located in non-clinical areas, should soon come back online.
As a precaution, all of the PCs were shut down after the infection was discovered. The infection affected computers used to admit patients, and the hospitals diverted emergency patients to other facilities for a short time.
The PCs did have antivirus software made by McAfee installed. McAfee, which received a sample of the Mytob strain infecting the hospital's PCs, said its up-to-date products do have the have the right signature to detect the worm.
It remains unclear how the PCs were infected. Mytob was discovered in early 2005, and most security products can detect it. A spokesman for the hospitals said on Monday an investigation is ongoing.