Internet Bandwidth Usage all of a sudden increased?

[Chrispy]

We've been using our Internet fine every month. 250GB of Bandwidth Usage is our limit. Each month we would reach CLOSE to it or close enough but never over.

Recently a new month has started, and in only TWO days we have reached 234GB/250GB of our usage. I don't know what we've been using to use over 200+GB in two days. All my Dad and I really do is just play games, talk to friends on skype, and surf the internet (typically Facebook/Youtube/Twitter) I don't know how in 2 days we can have that much.

Could most of the MB be used in buffering video/watching videos on youtube etc? It seems awfully surprising in 2 days we could have that much when we couldn't even pass it each month. Or could it be something else like DDos attacks if that's what they do?
@Dustin We do have wireless internet, there is a WPA2 password with WPS disabled so nobody can use our internet unless they know our password. So im sure nobody is using it!

We both never torrent anything, we used to in the past but never anymore and uninstalled all torrenting softwares etc. All we really do is just play games (Counter-strike/League of Legends) and surf the web. Counter strike probably only takes like 30GB of usage a month... So I really think the only thing that can be taking up a lot is buffering video and watching a lot of videos since my parents like to watch Netflix, Hulu, Youtube etc but for 2 days....I don't know.

[Dustin]

Do you have wireless Internet? Is there WPA2 password security with WPS disabled? If not someone may be using your internet. Also, I highly doubt that you use that much data unless someone is torrenting. Either someone in the house, or someone using your internet.

Edit: That's really odd then. I also find it odd that that game can take up so much data. My friend and I used our cell phone wifi hotspot to play PS3 Black Ops 2 for a few weeks and it hardly used any data. Is it possible that the ISP didn't start the month over on time and you are still seeing last month's data usage? One thing you can try is get network monitoring software. I haven't used any so I can't recommend anything but there should be something that can tell you where your data is going.

[Resnick]

Don't know. Enjoy the free internet so much.

[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.