How to track LAN usage? (AKA 'top for LAN')

Question

There's an evil application that is eating ALL my upload bandwidth (I'm brazilian, it's only ~35kbps) for like 80% of the time my PC is turned on.

I would like to know if there's any way to track this usage and discover what app is doing this.

Answer 1

What about nethogs? In my opinion, it is lot more humane. Lists which command/program using network and how much bandwidth for each of them, in realtime.

Install it in ubuntu/debian systems with:

sudo apt-get install nethogs

Run it to monitor your network interface like this:

sudo nethogs eth0

Answer 2

iftop is a console/shell-based program similar to top that can use the pcap library (also used by tcpdump and wireshark). It is available for Ubuntu from Universe.

sudo aptitude install iftop
sudo iftop

While running an upgrade on an ubuntu system:

With netstat, you can find out what process is connected to a particular port or IP. For ports, its a good idea to prefix with a colon.

sudo netstat -plantu | grep "some_port_number_or_ip_address"

For example, to look at open connections for ssh:

sudo netstat -plantu | grep :22
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2376/sshd       
tcp        0      0 10.13.37.122:22         10.13.37.105:59130      ESTABLISHED 4033/sshd: jtimberm
tcp6       0      0 :::22                   :::*                    LISTEN      2376/sshd 

You can also look for open port connections with lsof:

sudo lsof -i:22
COMMAND  PID       USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
sshd    2376       root    3u  IPv4   5613      0t0  TCP *:ssh (LISTEN)
sshd    2376       root    4u  IPv6   5615      0t0  TCP *:ssh (LISTEN)
sshd    4033       root    3u  IPv4  11608      0t0  TCP 10.13.37.122:ssh->10.13.37.105:59130 (ESTABLISHED)
sshd    4086 jtimberman    3u  IPv4  11608      0t0  TCP 10.13.37.122:ssh->10.13.37.105:59130 (ESTABLISHED)

You can get more information about the open files from lsof with -p PID.

sudo lsof -p 2376

(Lots of output from that suppressed)

Answer 3

ntop is your friend. Packages are in linux repos and macports.

Answer 4

In addition to using iftop to identify the address and port that's using bandwidth, you can use netstat to identify the process

sudo netstat -ntp

This will show all TCP connections open and the process name/id attached to each.

Answer 5

In my opinion, iftop's user interface is not well-designed. In practice there is hardly ever a need for viewing the IPs or hostnames in realtime. If I needed, a listing of all current connections, I would just go with netstat as jtimberman explained.

For my purposes, bmon is better suited than iftop. It has a very simplistic user interface with support for multiple interfaces and drawing of "graphs". Here is a screenshot:

If you do not need all the features bmon offers, bwm-ng might be the perfect tool for you. It only shows the current occupied bandwidth per interface -- no more and no less:

Answer 6

Wireshark is also a very good (multiplatform) app for monitoring network traffic. Here's a description from the site:

Wireshark is the world's foremost network protocol analyzer, and is the de facto (and often de jure) standard across many industries and educational institutions.

Answer 7

You could do this at the router level depending on your firmware. For example, if you use DD-WRT, you could track usage over time and by machine.

Answer 8

Install a firewall and, at least temporarily, make it block all outgoing connections. It should notify you when something tries to make a connection at which point you should have your culprit :-)

here is one of many articles online that gives you info on installing a firewall on ubuntu:
http://linux.com/news/enterprise/systems-management/8256-installing-a-firewall-on-ubuntu