Greater Manchester Police has been hit by the Conficker virus after an infected memory stick was plugged into the network.

The infection has left officers unable to carry out their own computer checks on criminals and suspect vehicles for over three days. All officers have been warned against using ‘unauthorised memory sticks' as investigators try to isolate the damage caused by the virus, according to the Manchester Evening News.

Greater Manchester Police has been disconnected from the Police National Computer (PNC), which is used to check names, criminal records and suspect vehicles against a national database. The force's incident log, which is used to record crimes, was not affected by the virus.

Dave Thompson, assistant chief constable of Greater Manchester Police, said that the public had ‘not experienced any difference in the service they received' as a result of the virus outbreak.

He told the MEN: “We have systems in place to ensure this does not affect our service to the communities of Greater Manchester. At this stage it is not clear where the virus has come from but we are investigating how this has happened and will be taking steps to prevent this from happening again.”

Jason Holloway, sales manager Northern Europe for SanDisk, said: “This underlines the fact that conventional USB flash drives are a key method for spreading these infections stealthily, and without the drive's user being aware – as both Ealing and Manchester councils found last year.

“Virus scanning has to extend beyond the PC to all types of removable storage.  Better still, employees should only be able to use authorised flash drives that include on-board anti-virus scanning.  This ensures that users can't turn off, disable or work around the protection, and would stop these infections from spreading.”

Anders Pettersson, CSO at BlockMaster, said: “It got into the police computer with an unsecured USB that used unauthorised autorun which is how it spread through the network. That is like the modus operandi of this virus, and why we created authorised autorun so nothing but activation can be run.

“This is kind of worrying, they have been offline for three days and they are thinking of costs that come with a hit against the police force. It would be a requirement for the CoCo standards and a requirement for secure USB usage, and port control on the system would be good, though if they had an approach to implement solutions it would put the problems in the spotlight and on the agenda.

“The good news is that there is a solution available, this is some comfort for branches but they seem to be responding to it now.”