Not too long ago the Stuxnet worm was discovered, and it seems that according to security analysts, if not dealt with quickly the Stuxnet worm could be exploited by hackers and allow them to remotely open the doors of maximum security prison.
It seems that the security systems in most American prisons, along with other industrial sites, are run by special computer equipment called industrial control systems (ICS). These are not only used to control the doors to maximum security prisons, but also used to control power plants, water treatment facilities and other critical national infrastructures.

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