Welcome to the weirdest question of 2014 so far.
Yesterday, a user's computer (Windows 7 Pro, on domain) started typing 56 at random intervals. I saw it sit there and type "5656565656" into notepad over the span of a minute or two, but sometimes it would go half an hour of not typing anything. The user claimed it would type "56" upon clicking on any cell in a blank Excel sheet at one point. Here's some facts:
- Replaced PS/2 keyboard with a USB one
- Uninstalled all HID drivers, rebooted to have them reinstall the necessary ones
- Uninstalled Microsoft Mouse & Keyboard software (for a wireless kit that doesn't exist anymore)
- Ran quick MalwareBytes scan; Clean
- Happens in any application: IE, MS Office, Notepad, etc.
- Happens with no applications open
- Happens in any user account
We've got Symantec Endpoint Protection updated on all computers. Nobody else is experiencing this. No Windows updates were applied in the days leading up to this happening. Many restarts have been performed. Something else installed is a document management software called OnBase, if anyone knows what that is, or if that helps.
Any other ideas I can pursue? It's not a hardware issue, not a virus, and I guess not a driver issue.