Software developer ProteMac has released the $US49.95 KeyBag utility, which it says "is designed for hidden monitoring of the computer activities."
"ProteMac KeyBag allows you to find out what other users do on your computer in your absence. You will find out, what was going on your computer in your absence: what was typed and the windows visited websites etc. This invisible employee spy surveillance tool records every keystroke to database file with user-friendly easy to use keystroke log viewer."
So when your boss insists that you don't need an anti-malware package on the Macs in the office, is it because he or she wants to keep something like KeyBag hidden?
Other commercial keystroke loggers designed for surveillance purposes include Spector Pro from SpectorSoft.
There are also hardware keystroke loggers that connect between the keyboard and the computer. While they are more obvious than the software approach, how often do you look behind your computer?