Source of Crazy Data Usage???

[eRondeau]

Bored tonight and checked my ISP’s Network Dashboard app (which I rarely look at). Shocked to see my M4 Mac mini has used 12,923GB of data in the last week and over 63,000GB in the last month. This must be wrong because this is an impossible amount of data to use. This Mac is usually left on (but not always) and other than the MacOS Tahoe 26.4 update last week it hasn’t done much except normal web surfing and emails. I don’t stream or download movies or music or use P2P. It’s only got a 512GB SSD and the app says I’ve downloaded the full storage capacity 125x this month! I’ve been keeping an eye on Activity Monitor for the last half-hour and its Network stats look totally normal. I have a 1Gbps Down / 30Mbps Up Cable connection.

I’ve also got a M3 iMac on the same network and it’s only showing 45GB for the month which seems entirely reasonable considering the MacOS update. My other devices on the network are well below that number.

So my question is — what’s the best way to confirm whether or not this ISP report is accurate, and how do I find out WTF is happening here?

 

[!!!]

Try checking Activity Monitor or maybe an app like Little Snitch mini (the free version, which just offers monitoring).

Also, at the ISP level, they can't detect which machine is using data, so you may be looking at data for your whole network. You could check to see if your router offers any kind of similar monitoring features and see if it's some other device, sometimes smart TVs and the like upload tons of data.

 

[eRondeau]

Try checking Activity Monitor or maybe an app like Little Snitch mini (the free version, which just offers monitoring).

Also, at the ISP level, they can't detect which machine is using data, so you may be looking at data for your whole network. You could check to see if your router offers any kind of similar monitoring features and see if it's some other device, sometimes smart TVs and the like upload tons of data.

Thank you! I’ve downloaded & installed Little Snitch Mini and we’ll see what tale it tells… but the more I think about it, it must be an error at my ISP. ChatGPT says that heavy home internet use is 1TB/month and very few families exceed 2TB/month. Meanwhile my little Mac mini exceeds 60TB/month? No possible way. And I’m not sure how it works, but my ISP’s app can see every device on my wired+wireless home network — computers, iPhones, iPads, security cameras, Alexas, smart plugs/bulbs/switches — and gives detailed data usage reports for each of them.

 

[Basic75]

Shocked to see my M4 Mac mini has used 12,923GB of data in the last week and over 63,000GB in the last month.

Could it be 12-comma-9 GB instead of 12-thousand GB?

 

[FreakinEurekan]

12,923GB of data in the last week and over 63,000GB in the last month

Almost looks like they’re using a comma as a decimal separator, common in some parts of Europe (e.g. 12,923 vs 12.923). But the fact that it’s only affecting this one device is certainly odd.

 

[eRondeau]

No mistaking these numbers… one for the week and the other for the month.

 

[Basic75]

Whoa. I'd monitor the traffic and look for malware.

 

[okkibs]

You can look at the activity monitor on the Mac and see what the network tab says for downloaded data. It tells you the usage per app so you can narrow it down immediately. The data only lasts until a reboot where it's reset again and starts fresh so if you reboot often you might not see anything.

Generally for monitoring you might be able to get a widget/app for your router connection to check throughput in real-time if your ISP offers anything. I use my own Ubiquiti Unifi equipment (instead of the ISP router) that has a status monitor where I can always see the current download and upload for my internet connection.

Since you are correct that your Mac can't even store all this data on the small internal SSD it might just be an incomplete stuck Apple macOS update process that keeps downloading the same Mac update over and over again. Check your macOS software version, you might not be on the latest macOS 26.4.

 

[chown33]

Other than the Network data in Activity Monitor, there's also the command-line 'nettop'. Read its man page for details.

I'd set up 'nettop' to run for a 24-hr period, collecting data to a file. Then compare that file's record to the ISP's 24-hr record of network traffic for the machine. If you don't want to write to a file, run it in its own Terminal window, and keep it running for 24 hrs.

 

[eRondeau]

Try checking Activity Monitor or maybe an app like Little Snitch mini (the free version, which just offers monitoring).

Thank you again for suggesting Little Snitch Mini. I tried the free version and it's impressive; its instantaneous transfers agreed with Activity Monitor in that my data use was entirely typical. Yesterday I subscribed for a full year which adds ongoing totals and so far no surprises. I believe my ISP's app has gone crazy, besides if I was using 65,000GB/month I'm sure my ISP would be sending someone to my house to snip the wire. Thanks for the great suggestions everyone!

 

[AbeLincoln1984]

Thank you again for suggesting Little Snitch Mini. I tried the free version and it's impressive; its instantaneous transfers agreed with Activity Monitor in that my data use was entirely typical. Yesterday I subscribed for a full year which adds ongoing totals and so far no surprises. I believe my ISP's app has gone crazy, besides if I was using 65,000GB/month I'm sure my ISP would be sending someone to my house to snip the wire. Thanks for the great suggestions everyone!

Sometimes people find out they've been mining bitcoin or something in the background.

Have fun.