Unknown auto typing. Malware?

Question

My Macbook started to autotype by itself (as if you had the space bar pressed all the time).
This happened at first with random letters, and finally with all users in all contexts, typing spaces continuously. Even at restart in the login window, with no users still logged in. I could not even type my password, as the spaces kept coming in!
I could not identify a process, daemon or script that was causing it, as it was nearly impossible to even type my admin password.
The solution was to reinstall OSX 10.5 with my original disks, preserving the accounts and settings. Everything went back to normal, but I'm still nervous about not having found the root cause.
It's a brand new MacBook with latest updates, and, yes, I downloaded and run some utilities from the Internet, as I always do. I doubt is malware, but it may be.
My questions are:
1)Anyone ever experienced something like this?
2)Any idea on how to identify/pinpoint/log what's going on if the symptoms start again? I used Activity Monitor and the Console but could not find anything obvious there.
Thanks!

Answer 1

Welcome to Apple Discussions!
The most common cause is dust on the keyboard or accidentla keyboard depression from the palm of your hand. The next most common cause is an errant Universal Access setting being setup by an accidental keyboard stroke. Check the Universal Access shortcuts in Apple menu -> System Preferences -> Universal Access to see if it is likely any of those were depressed, or Apple menu -> System preferences -> keyboard and mouse -> full keyboard access shortcuts.
Sometimes if you have speech recognition turned on a keystroke can be mapped to another keyboard command by accident.
If iChat Screen Sharing was enabled in a certain chat, that gives access to someone else to access your keyboard directly and act on your machine. But you have to give them permission for that to happen. Same with certain VPN and VNC programs and Remote Access programs.
As there are no known Mac OS X viruses in the wild and only trojan horses, you'd be the first this has happened to if none of these solutions appears to solve it.
Message was edited by: a brody