Describing Conficker, security researchers state that it's a PC worm, which attacks Microsoft's Windows operating system. As per the estimates, Conficker can potentially facilitate its creators take control over 7 Million infected PCs in over 200 countries.

Crewe's Leighton Hospital and Northwich's Victoria Infirmary come under the Mid Cheshire Hospitals NHS Foundation Trust. The IT professionals working in these hospitals spotted the virus on January 20, 2010. They noted that its infection disseminated to about 9% of the systems the Trust owned. It was, however, disclosed that the worm did not affect any major clinical system, as patient appointments and care were unaffected.

Furthermore, according to the sources, Conficker entered into the hospital's computers through a contaminated image dispatched via the Picture Archiving and Communication Systems, basically a digital x-ray facility. However, according to the Trust, initial probes suggest that the Conficker entered the systems through a USB device.

A few hospitals have informed the Conficker Working Group that most of their computers were successfully amended; however, they were not successful enough to entirely eliminate the worm. Also, a few IT executives at the hospitals believe that the notorious resilient worm is possibly residing inside medical devices and OEM equipments controlled by their vendors.

In the wake of this point, the experts commented that it was possible for the virus to hide inside a harmless system kept at the hospital for visitors' use, and off the core IT network in the premises. However, external specialists as usual are unable to figure out the place where any virus stays inside the computer network of a healthcare center. Nevertheless, they are capable of confirming its presence as it repeatedly sends out a signal, which can be captured.

In the meantime, it has been lately speculated that The Christie NHS Foundation Trust along with similar nearby trusts had also been hit by the worm, although Christie denied the allegation.