9. E-mail flames from some guy named "Fluffy."
8. Traces of kitty litter in your keyboard.
7. You find you've been subscribed to strange news groups like alt.recreational.catnip.
6. Your mouse has teeth marks in it... and a strange aroma of tuna.
5. Hate-mail messages to Apple Computers, Inc. about their release of "CyberDog."
4. Your new ergonomic keyboard has a strange territorial scent to it.
3. You keep finding new software around your house like CatinTax and WarCat II.
2. On IRC you're known as the IronMouser.

and the #1 Sign Your Cat Has Learned Your Internet Password...

1. Little kitty carpal-tunnel braces near the scratching post.