So basically my site was unaccessible and I went to logs folder to see what's wrong and noticed a lot of weird requests from various IPs:
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
209.141.45.189 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
209.141.45.189 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:45 +0300] "GET / HTTP/1.0" 200 6189 "-" "Google Bot"
185.220.100.252 - - [30/Mar/2020:20:23:56 +0300] "GET / HTTP/1.0" 200 6344 "-" "Google Bot"
209.141.45.189 - - [30/Mar/2020:20:23:56 +0300] "GET / HTTP/1.0" 200 6344 "-" "Google Bot"
162.247.74.206 - - [30/Mar/2020:20:23:56 +0300] "GET / HTTP/1.0" 200 6344 "-" "Google Bot"
155.4.117.13 - - [30/Mar/2020:20:23:56 +0300] "GET / HTTP/1.0" 200 6344 "-" "Google Bot"
I wonder if it's some kind of attack.
Did some whois lookup, for example this ip 185.220.100.252 is from Germany, "tor-exit-1.zbau.f3netze.de"
How can I protect server from such attacks?
They do like thousand of requests per minute and I can't access my own site.
Error.log says:
AH00161: server reached MaxRequestWorkers setting, consider raising the MaxRequestWorkers setting
(I'm not a webmaster, I host a small site for my needs and have no idea how to react.)
This is exactly the scenario that fail2ban was invented to cover. I suggest you look into that here: https://www.fail2ban.org/wiki/index.php/Main_Page
Likely the "badbots" jail would take care of this immediately, and if not it wouldn't be difficult to code a custom jail/filter set to take care of it.
For now, seeing how they IP's seem to be limited, I suggest banning those IP's via iptables:
This is what fail2ban does of course (adds IP's to iptables), but fail2ban does it automatically. It would have protected you from this attack without your even noticing.