I got a letter from my ISP a while back, complaining about a movie I was supposedly downloading. At first I wrote it off until I later saw my roommate watching that movie, I asked him about it, and he admitted to downloading it. I asked him to refrain from using bittorrent illegally, and he said he would, but I recently saw him shuffling torrents around in uTorrent. Now, I'm the only one who pays for the connection, and it's all in my name. I talked to him about it again, but I'm wondering if there's a way I could setup a Wireshark script something to alert me if/when it finds bittorrent traffic.
I don't have a direct way via wireshark or that directly, however - I do have a few options for you.
-You could set-up a DNS server for your place and route all traffic through it. You can limit certain types of connections and various websites. Let's suppose you knew he used the piratebay, block *.piratebay.* or whatever. (other common ones: 1337, publicbt, openbittorrent, h33t, istole.it, desync).
1: Block Sites / Protocols
Just as easily, you could block sites (or ports) via most routers. This could be accomplished with blocking common bittorrent ports (and if you experience issues with your normal web use, you could adjust this easily).
2: Block their access
Sounds like if your name is on stuff, they need to listen to you. #1, if you are splitting the cost of service - stop accepting their money. That then covers you for later disallowing them access. You can either MAC filter or change the codes. However - this is limited in usefulness as someone with physical access can change settings or do a full reset (thusly doing nothing).
Create a written contract. Enumerate what you want to happen. 1) No torrenting or illegal downloading of any kind. 2) They are responsible for all instances of #1 3) If #1 is broken, you have the right to discontinue service at will or institute network monitoring &/or network limitations. And so-forth. If they break it, move to Very Extreme
Cancel your service to the ISP. Instead, if you are able, tether your phone for your needs (basic needs would be okay, but streaming video or anything would not work well). If they need it, they will either go elsewhere or put it under their name (unless their a slime-ball and try to impersonate you).
Hope their is some value there for you. Another option could be setting up a PC or tomato router and having that do some packet shaping - but I do not have enough experience with that to provide useful comments.
This is best done on the router.
In OSes with a solid and configurable network layer it's possible to monitor everything with the built-in kernel firewall, on "home routers" with custom systems it may be less straight forward or even impossible. Your best bet it to install a "proxy" machine that does routing with BSD or Linux (there are router-distros which are good for this) that will monitor the network and notify you via email when needed.