On 28.07.21 14:44, Jonathan Billings wrote: > 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. > > TCP wrappers (hosts.allow/deny) are deprecated now. Its still supported in EL7 (sshd example) ldd /usr/sbin/sshd |grep wrap libwrap.so.0 => /lib64/libwrap.so.0 (0x00007fcc483ee000) but not in EL8 anymore. EL8 is based on F28/29 -> https://fedoraproject.org/wiki/Changes/Deprecate_TCP_wrappers For the question above (for EL7): only services that are compiled against libwrap uses hosts.deny everything else will be reachable (if iptables does not drop it). For EL8, as depicted in the above URI: systemd provide a similar functionality ... -- Leon