[ubuntu] Bandwidth monitoring by device

I have a DSL modem router with WiFi. Five people share the bandwidth. For the first time ever, I'm getting a notice from the ISP that we have used more than 600gig in the billing period. Bandwidth usage is now about 20-30 gig a day. I need to find some app or software (CLI is good, too.) that can show which device is sucking up the bandwidth. Typical bandwidth is 3-5 gigs a day. If our WiFI has been , I need to figure that out before asking family to stop using so much bandwidth.

I've tried: nload (it's confusing, I'm not a tech guy)
I've tried iptraf (it's not showing by device and has to run as admin/sudo, leaving the OS in a state of vulnerability, as I have to leave it on all the time).
I've looked at Network Tools, but caot find how to know which devices are using the bandwidth.

What I want is an app/software that monitors usage by coected device and shows it's usage over a period of 8 or 12 or 24 hours. It needn't be graphical or GUI, but that's a niceness if it's available.