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This reads a bit far fetched but McAfee reckons that stickykeys, a tool designed to aid access, could aid access for malicious users. If you replace the stickykeys .exe with command prompt - cmd.exe - you can launch the comand line even when locked out of the machine just by hitting shift 5 times.
But, as Microsoft points out, in order to set this up, you'd need admin access anyway.