slackbuilds/network/nethogs

NetHogs is a small 'net top' tool. Instead of breaking the traffic
down per protocol or per subnet, like most tools do, it groups
bandwidth by process. NetHogs does not rely on a special kernel
module to be loaded. If there's suddenly a lot of network traffic,
you can fire up NetHogs and immediately see which PID is causing
this. This makes it easy to indentify programs that have gone wild
and are suddenly taking up your bandwidth. 

Depends on libcap, available at SlackBuilds.org