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My internet connection is very slow. I suspect someone in the network is using a BitTorrent client which takes huge amount of bandwidth.

Is there a way to detect who is using my bandwidth (network sniffing tools etc)?

I should have pointed out that I have no access to the router, what I am looking for is a way of detecting someone's MAC/IP if she uses Bittorrent.

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Do you have access to a edge device? – Not Kyle stop stalking me Feb 21 '13 at 21:47
up vote 1 down vote accepted

Here's one comprehensive article. It suggests four approaches:

  • Port-based analysis
  • Protocol-based analysis
  • Client-based analysis
  • Behavioral analysis
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The link doesn't work anymore. – Jakub Sep 17 '14 at 12:10
@Jakub thanks! Updated the link – sm4rk0 Sep 17 '14 at 15:56

Ryan's answer is great, though I would start by maintaining a very strict access policy on your network. Use MAC address filtering and use a very strong WPA2-PSK key. Essentially, preventing unwanted traffic starts with preventing unwanted users.

QoS can be difficult to configure if you are totally unfamiliar. Can I have your router model?

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Don't worry about who's doing it and stop them instead - if you log into the router, disable upnp, set the default to 'deny' for all ports and then only enable the ones you use (the services are normally listed in most domestic/soho routers) and see if anyone complains.

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thanks, I should have pointed out that I have no acess tothe router – mLar Feb 22 '13 at 8:29
Without access to the router you're pretty much done since you can't stop them anyway. You can find out if the router is busy or not (and normally it has lights for the wired ports so that may tell you if they're busy). – James Snell Feb 22 '13 at 8:44

If you have access to your router you can see what traffic and what ports are being used. Additionally you can blog P2P inside most routers and see if your bandwidth improves. Is this a home or work network? Have you asked the users? QoS would be your best option if someone is using it and you don't want to completely shut it down. You can flag P2P traffic as bulk and give it a very low priority.

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