I've had 3 situations where my place of work was under DoS attack, in the 3 cases I managed to identify an email address and reached out asking why they are doing it, and if they want to talk about our backend. In 1 case, the "attack" was a broken script by someone learning how to program, the other two were real attacks and one of them just immediately stopped once they knew we knew who they were, the other actually wanted to chat and we emailed back and forward a bit.
99.99% of the time a DoS is someone who is bored. Talking to them tends to work.
Edit: there's some questions about the situations so I'll expand:
- The first was not a real attack, and they were doing the network calls through their authenticated API key. This was early days of a YC startup so of course there was no rate limiting in place. In this case I exchanged 2 or 3 emails and after they sent me their python script I sent them back a patch and they finished their scraping without bringing us down. Never heard from them again
- The second was at a different company, we were getting targeted to distribute email spam, because at the time we'd allow people to invite their colleagues as members of their account, and some people associated with casinos based out of Macau automated a way to spam their casinos by putting the URL in the name of the account, which went out in the email notification. I contacted one of the admin emails of one of the casinos I found and they stopped and disappeared. In this case we also locked all their accounts and prevented further logins + emailed them to reach out to support if they thought it was a mistake.
- The third one was more difficult, they weren't using any account, so all we had was network. At some point on the second day though they changed how they were sending some of the calls, and by mistake or not leaked their Telegram username. I installed telegram and talked to them, they trolled me a little bit, but stopped very quickly and didn't start it again. This one was very amusing to people in my company because I had told them this approach would work but a few of the big wigs didn't want me to do it (they didnt have any reason other than "obviously won't work to just talk"). I just did it anyway.
To be clear, you shouldn't reach out with some threats or how you're so good that you found them. My approach is of genuine curiosity, and my literal first message to the telegram person was:
"Hello, how is it going? I work at <companyname> and we're seeing a load of requests originating from your user here on telegram. Does this make any sense to you or do you think I might have the wrong person?"
That's it!