Do you know how to hack computers?

I always hear how “everyone” knows how to hack things, and you need to have top-notch security for everything (even if it’s not important) because even mothers (the stereotypical kind) can get into that easily. So I’m interested: Just how many jellies can hack something?

If you can, what can you hack – are we talking a hotmail account or a Swiss bank? Where/how did you learn to do this?