I have these entries in /var/log/nginx/access.log:
107.155.152.109 - - [22/Mar/2018:19:20:54 +0000] "GET / HTTP/1.0" 301 193 "-" "-"
162.216.152.56 - - [22/Mar/2018:19:21:40 +0000] "GET / HTTP/1.0" 301 193 "-" "-"
60.191.48.204 - - [22/Mar/2018:19:21:52 +0000] "GET / HTTP/1.0" 200 17582 "-" "-"
they look suspicious to me, but my knowledge of this area is limited. What's going on? There's even several others from 107.155.xxx.xxx
2 of the addresses appear on this site as reported: https://www.abuseipdb.com/check/. They are 162.216.152.56 and 60.191.48.204, apparently Jacksonville, U.S. and China.
I've configured fail2ban as described here as I'm on Digital Ocean with Ubuntu 14.04, but nothing in the fail2ban log.