A mistake by an EDS computer operator caused the crash that prevented 40,000 PCs at the Department for Work and Pensions from accessing core systems between 22 and 26 November, EDS has admitted.
The fault was eventually identified and corrected by a team of EDS and Microsoft engineers working with the ministry's staff.
EDS, the lead contractor for the DWP’s systems, said most functions had been restored by the morning of 25 November, with a full service available by 26 November.
EDS confirmed that the cause of the problem was an error by an EDS computer operator, which saw a software upgrade applied to computers that were not intended to receive it. This caused "some desktop computers to stop functioning appropriately", said EDS.
In a bid to prevent the problem happening again, EDS has enhanced its change management procedures and introduced more checks by senior EDS engineers and management staff when such upgrades are implemented.