Software to show amount of data transfer of each process

Solution 1:

You could use nethogs to see the speed of transfer for each process.

sudo apt-get install nethogs

Run it in terminal by running sudo nethogs but if you have more than one network device, you may need to specify it like so:

sudo nethogs eth0
sudo nethogs eth1  
sudo nethogs wlan0  
sudo nethogs wlan1  

A picture of nethogs working with a chrome opening a webpage:

You also have bmon which shows you ethernet devide usage.

sudo apt-get install bmon

and just run it like sudo bmon it will show you all network devices are their usage

Solution 2:

You can use a command line tool called nethogs. First install it:

sudo apt-get install nethogs

Then call it on the interface.Like this for Ethernet interface:

sudo nethogs eth0

It shows at what speed, processes are sending and receiving data.It may help you to find the unusual data transfer.