I would have known it shouldn't have been there, and maybe being plugged into the keyboard would have given me a clue, but I don't know.
This reminded me of a Technology Skills Library Staff Should Have list Sarah posted at ALA Learning (via). I wouldn't expect any staff to recognize a keylogger, but staff do need to be familiar enough with library equipment to recognize when something gets out of whack - printer not working right, copier making funny noises, website down, a monitor cable unplugged, or a foreign device plugged into a computer.
I like her list a lot, and am going to spend some time merging it with the idea from the Wilmington (MA) Library to break tech knowledge up into different levels to form a tech skills matrix.
Tech competencies is a topic I keep revisiting, because it is something that continually evolves - identifying keyloggers are just the latest addition.