automaticky blokuje IP adresy po urcitem poctu nespravnych prihlaseni k dane sluzbe.

1. zjistime si jmeno pozadovaneho jailu

   $ sudo fail2ban-client status
   Status
   |- Number of jail:      4
   `- Jail list:   nginx-botsearch, postfix, postfix-sasl, sshd

2. a zablokujeme pro danou IP adresu

   $ sudo fail2ban-client -vvv set <jail> banip <IP adresa>                                                                                                         
    +  289 7F11A493AB80 fail2ban.configreader     INFO  Loading configs for fail2ban under /etc/fail2ban                                                                                         
    +  290 7F11A493AB80 fail2ban.configreader     DEBUG Reading configs for fail2ban under /etc/fail2ban                                                                                         
    +  290 7F11A493AB80 fail2ban.configreader     DEBUG Reading config files: /etc/fail2ban/fail2ban.conf                                                                                        
    +  291 7F11A493AB80 fail2ban.configparserinc  INFO    Loading files: ['/etc/fail2ban/fail2ban.conf']                                                                                         
    +  291 7F11A493AB80 fail2ban.configparserinc  TRACE     Reading file: /etc/fail2ban/fail2ban.conf                                                                                            
    +  292 7F11A493AB80 fail2ban.configparserinc  INFO    Loading files: ['/etc/fail2ban/fail2ban.conf']                                                                                         
    +  292 7F11A493AB80 fail2ban.configparserinc  TRACE     Shared file: /etc/fail2ban/fail2ban.conf                                                                                             
    +  292 7F11A493AB80 fail2ban                  INFO  Using socket file /var/run/fail2ban/fail2ban.sock                                                                                        
    +  292 7F11A493AB80 fail2ban                  INFO  Using pid file /var/run/fail2ban/fail2ban.pid, [INFO] logging to /var/log/fail2ban.log                                                   
    +  293 7F11A493AB80 fail2ban                  HEAVY CMD: ['set', 'postfix-sasl', 'banip', '212.70.149.57']                                                                                   
    + 1474 7F11A493AB80 fail2ban                  HEAVY OK : 1
    + 1475 7F11A493AB80 fail2ban.beautifier       HEAVY Beautify 1 with ['set', 'postfix-sasl', 'banip', '212.70.149.57']                                                                        
   1
    + 1475 7F11A493AB80 fail2ban                  DEBUG Exit with code 0

3. a overime

   $ sudo fail2ban-client status postfix-sasl
   Status for the jail: postfix-sasl
   |- Filter
   |  |- Currently failed: 0
   |  |- Total failed:     0
   |  `- Journal matches:  _SYSTEMD_UNIT=postfix.service
   `- Actions
      |- Currently banned: 1
      |- Total banned:     1
       `- Banned IP list:   212.70.149.57