On Jul 27, 2021, at 16:43, H <agents at meddatainc.com> wrote: > > |Running CentOS 7. I was under the impression - seemingly mistaken - that by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban all attempts from that network segment to connect to the server, ie before fail2ban would (eventually) ban connection attempts. > > This, however, does not seem correct and I could use a pointer to correct my misunderstanding. How is hosts.deny used and what have I missed? > > Is it necessary to run: > > iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP > > to drop incoming connection attempts from that subnet? Upstream openssh dropped support for tcp wrappers (hosts.deny) a while ago but RHEL had patched support back in for a while, but I believe it isn’t supported anymore. For what it’s worth, if you use the fail2ban-firewalld package, it uses ipset rather than iptables, which is more efficient. -- Jonathan Billings