Hello, Some one is using bandwidth in my VPS and I don't know who . . . I cannot find anything in cPanel "list bandwidth", yet my VPS control panel shows that the bandwidth is used . . . how will I track that who is the user??? Thanks.
Your best bet is in your site's access log to see where the requests are coming from. I'm not sure if you can view that from CPanel.
actually you should be concerned more that your server is breached. This thing is serious as you don't know what the hacker is doing in your server fix it or get help from someone who can fix it for you ASAP