Where did outgoing 2TB traffic come from in a few hours?

Question

Network administration

There is VDS. Not used, I pay for it just like that. I took it to practice deploying projects.
Today, a message has fallen that 2tb (included in the tariff) of traffic has been used up.
There is a Vesta panel. Rebooted.

What could have caused this?
After the reboot, everything returned to normal, turned off the mail server just in case.

Answer 1

Not advertising, but very similar to this case.
UPDATE: One of our clients had a similar one. Outgoing SYN traffic suddenly increased.

Answer 2

Perhaps the memcached on the VDS is sticking out, and someone has arranged a memcached-amplifier from your VDS . So check if something superfluous is sticking out, and if it sticks out, block it at least with a firewall.

Answer 3

For starters, you should look at least in netstat what creates this traffic for you. And then dig and look.