Cause of router slowdown? Can one computer do it?

[Taiguy]

I'm using a WRT54G. Alright so here's the situation.

I've been using my WRT54G with DD-WRT v23sp2 since it came out and have been really happy. Around 2-3 weeks ago my roommates and I noticed that our internet was slow. REALLY slow. Pages would take half a minute or more to load. SSH into my school's network gave download speeds of 3 KB. Completely unacceptable. We thought this might be an effect of us torrenting and Comcast's new packetshaping methods. We toned down our connection limit to something miniscule... 8 global connections. We still got REALLY slow web browsing. If we rebooted the router, it would blaze along at normal speeds for a minute or two before returning back to a crawl.

So my first hypothesis of Bittorrent being the culprit isn't looking to credible. Even if comcast is shaping bittorrent traffic, that shouldn't cause our HTTP to die, nor should it lock the router so I can't access it through the web.

I wondered if the router was going a bit wonky. I reset it to factory defaults and then loaded up the newest DD-WRT v24 RC4. Same symptoms.

Here's the latest bit. I've decided to cut one of my roommates off completely to see if it's one of the computers on the network causing the slowdown. Out of the 4 of us that live in the apartment, 1 hates computers and lives without the internet for the most part, another is never around, so that leaves 2 that use our connection extensively. That would be myself and another. Since cutting the other person off I've noticed I'm torrenting at 10x the speed I was going before IN CONJUNCTION WITH browsing at normal speeds.

Is there anything that would cause one computer to slow down an entire network if it's connected? He says he only keeps 4-10 global connections for bittorrent, but I've already established that bittorrent isn't slowing me down at all. I do know that he tried installing the WPA 2 update for Windows XP *around* the same time we noticed the slowdown. Could a driver issue somewhere be causing one wireless NIC to be sending junk packets and bringing everything down?

All I know is that without him on the network everything is MUCH FASTER. Need help, I'm out of ideas.

 

[Dangman]

He could be infected with a virus, worm or trojan. Do a scan for those, preferably not connected to the net, and see if anything shows up. Also scan for spyware, adware and other malware.

After all that and if your connection is still slow, then uninstall the new drivers/update your friend installed and see what happens.

And what WPA2 update are you talking?

 

[Taiguy]

And what WPA2 update are you talking?

I think this is what he found. http://support.microsoft.com/kb/893357

so virus/malware? what could malware do to clog the entire network? is there a way to monitor traffic through one of the router interfaces?

 

[RoBo]

He might have a torrenting program running as a service, eating your bandwith.