PawSense (Sadly, not available for Macintosh.)
When cats walk or climb on your keyboard, they can enter random commands and data, damage your files, and even crash your computer. This can happen whether you are near the computer or have suddenly been called away from it.
PawSense is a software utility that helps protect your computer from cats. It quickly detects and blocks cat typing, and also helps train your cat to stay off the computer keyboard.
Mister Gato has never managed to successfully execute a command on any of our machines, but he routinely turns on Caret Browsing in Firefox by pressing the F7 key on his way to his favorite perch, the keyboard hutch on our computer desk.
He has also sent enough garbled IMs that people who regularly talk to me or my wife now respond to a string of nonsense characters with "Hi, Mister Gato!"