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. – NetHogs (http://nethogs.sourceforge.net/)

NetHogs is not available in official RHEL/CentOS repositories, so let us add EPEL repository to install NetHogs:

# rpm -Uhv http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm

Then install NetHogs using the command:

# yum install nethogs -y