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Updated Servers on the network of NHS Leeds were struck down by the Conficker worm late last week.

The malware infection struck on Friday and forced administrators to take a handful of infected servers offline, in phases, in order to apply deworming tools. Trust PCs were not infected by the attack, which a leaked memo (extract below) blamed on the connection of an infected laptop to the network.

NHS Leeds confirmed the minor outbreak, adding that its clean-up operation should be finished by the end of the week. It promised to revamp its patching strategy in the wake of the incident.

A spokesperson for NHS Leeds said, “We can confirm that some of our servers have been affected by the Conficker virus. We’re currently disinfecting the infected servers in the system and expect this process to be complete by the end of the week.

“Fortunately our PCs themselves remain unaffected at this time and the virus has not affected our clinical systems. We have managed to reduce the impact on all other services so that there has been minimal disruption to the organisation. To reduce the risk of future viruses we have a patching strategy in place.”

Rik Ferguson, a security consultant at Trend Micro, expressed surprise that the infected servers did not neutralise the threat as soon as the initial infection was attempted. He speculated this might be because legacy systems for which it's difficult to obtain security protection were infected.

"I would certainly hope that the machines had been patched against the vulnerability that allowed the worm to spread across the internet so widely last year," Ferguson told El Reg. "However, if the malware is introduced to a network through an infected USB stick (or infected laptop) then it can also (depending on the variant) propagate through network shares and brute force password attacks."

"This memo would seem to indicate that it was that particular variant as it mentions accounts being locked out, this is probably through the brute forcing of passwords. This lockout policy is sensible and will have helped to minimise damage."

Problems at Leeds follow a much more serious outbreak involving Greater Manchester Police that resulted in a decision to disconnect force computers for four days while a clean-up operation was mounted.

Conficker was first detected in November 2008. Initially the worm spread using a Microsoft Windows vulnerability but other tricks in its armoury, in particular its ability to spread from infected USB sticks, have become its main route for infection.

Over recent weeks, UK public sector IT systems, particularly in hospitals, have been struck down by secondary infections. The outbreak in Leeds comes a little over a fortnight after the malware infected systems over the Pennines at Mid Cheshire NHS Trust. Conficker infected 85 PCs (or 3 per cent) of machines across the trust's network. Mid Cheshire told E-Health Insider that clinical systems were unaffected by the outbreak, which had no impact on patient care or appointments. ®

Bootnote

NHS Leeds is not related to Leeds Teaching Hospitals NHS Trust, a similarly named organisation not affected by the outbreak.

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