[CentOS] hosts.deny, fail2ban etc.

Wed Jul 28 12:44:17 UTC 2021
Jonathan Billings <billings at negate.org>

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