• ​https://linkmeup.ru/blog/11.html​

• ​https://habr.com/ru/post/307252/​

Tools

iptables

• ​https://www.booleanworld.com/depth-guide-iptables-linux-firewall/​

• ​https://habr.com/ru/sandbox/18975/​

List rules in all chains (default table is filter, there are mangle, nat and raw tables beside it):

$ sudo iptables -L -n --line-numbers [-t filter]

Print rules for all chains (for a specific chains):

$ sudo iptables -S [INPUT [1]]

fail2ban

• /etc/fail2ban/filter.d - filters which turn into user-defined fail2ban iptables rules (automatically).

Status:

$ sudo service fail2ban status
$ sudo fail2ban-client status
$ sudo fail2ban-client status sshd

Unban:

$ sudo fail2ban-client unban --all
$ sudo fail2ban-client set sshd unbanip <IP>