Internet Bandwidth Usage all of a sudden increased?

[tesseract]

Perhaps you have heard of picking a lock. There are software programs (typically used by people doing something they don't want traced back to an account with an ISP that they pay for. EG downloading music or movies or over the top porn) that do the equivalent of picking a lock, whether the lock is WEP, WEP PSK etc. The newer wireless encryption keys are longer and therefore harder to pick, but that just means 30 minutes sitting in a car parked in front of your house instead of 5 minutes.
If you suspect that someone else is logged into your wireless router, get out the instructions for that router and look at the MACs connected. Each computer has a Media access control address that is a 48 bit binary number. It acts like an electrical address to send packets to by associating this 48 bit serial number to the IP address your ISP assigns you. If there are more than the two that belong to you and your father logged into the router, boot one off and add it to restricted MACs on the router.
Most routers also have a means of restricting access so you can tell it to ONLY accept your machine and your dads. This keeps goffballs off even if they crack your WEP key.
If ONLY your two machines show up on the log, then one or both of you have acquired a malware, so that your computer is doing a lot of work remotely for someone else somewhere on the internet.
If your computer is sending out 30,000 spam emails a day for someone, you can chew up a lot of bandwidth. Reload windows on the affected machines.