Fail2Ban : Intrusion Prevention System2024/06/20 |
Install and configure [Fail2Ban] that is the kind of Intrusion Detection System. |
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[1] | Install Fail2Ban. |
# install from EPEL [root@dlp ~]# dnf --enablerepo=epel -y install fail2ban whois
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[2] | The default configuration is defined in [/etc/fail2ban/jail.conf]. The default values may change with package updates, so if you want to change the settings, create a [jail.local] file and modify it. |
[root@dlp ~]#
vi /etc/fail2ban/jail.conf # line 87 : ignore your own local IP #ignoreself = true # line 92 : possible to add ignored networks #ignoreip = 127.0.0.1/8 ::1 # line 101 : number of seconds that a host is banned # - 1m ⇒ 1 minutes # - 1h ⇒ 1 houer # - 1d ⇒ 1 day # - 1mo ⇒ 1 month # - 1y ⇒ 1 year bantime = 10m # line 105 : A host is banned if it has generated "maxretry" during the last "findtime" findtime = 10m # line 108 : "maxretry" is the number of failures before a host get banned maxretry = 5 # line 178 : destination email address if enabling email notification destemail = root@localhost # line 181 : sender address if enabling email notification sender = root@<fq-hostname> # line 263 : default action # - %(action_)s ⇒ ban only # - %(action_mw)s ⇒ band and email notification (includes Whois info) # - %(action_mwl)s ⇒ band and email notification (includes Whois info and logs) action = %(action_)s
[root@dlp ~]#
vi /etc/fail2ban/jail.local
# create new
# possible to override the default values
[DEFAULT]
ignoreip = 127.0.0.1/8 ::1
bantime = 1d
findtime = 5m
maxretry = 5
destemail = root@localhost
sender = root@dlp.srv.world
systemctl enable --now fail2ban
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[3] | If you want to monitor services, add settings. (Default is unset) As an example, set the SSH as the service to be monitored. |
[root@dlp ~]# fail2ban-client status Status |- Number of jail: 0 `- Jail list:
[root@dlp ~]#
vi /etc/fail2ban/jail.d/sshd.conf # create new [sshd] enabled = true # possible to override the default values by service bantime = 600 findtime = 3m maxretry = 5 action = %(action_mw)s
[root@dlp ~]#
systemctl reload fail2ban
# show status [root@dlp ~]# fail2ban-client status sshd Status for the jail: sshd |- Filter | |- Currently failed: 0 | |- Total failed: 0 | `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd `- Actions |- Currently banned: 0 |- Total banned: 0 `- Banned IP list: # some hosts that exceed the threshold are banned [root@dlp ~]# fail2ban-client status sshd Status for the jail: sshd |- Filter | |- Currently failed: 1 | |- Total failed: 6 | `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd `- Actions |- Currently banned: 1 |- Total banned: 1 `- Banned IP list: 10.0.0.203 # actual ban action is controlled by Firewalld [root@dlp ~]# firewall-cmd --list-rich-rules rule family="ipv4" source address="10.0.0.203" port port="ssh" protocol="tcp" reject type="icmp-port-unreachable" # if enabled email notifications, you will receive the following email [root@dlp ~]# mail s-nail version v14.9.22. Type `?' for help /var/spool/mail/root: 3 messages 1 new 2 unread U 1 Fail2Ban 2024-06-20 16:05 21/546 "[Fail2Ban] sshd: start" 2 Fail2Ban 2024-06-20 16:06 27/665 "[Fail2Ban] sshd: banne" N 3 Fail2Ban 2024-06-20 16:10 92/3367 "[Fail2Ban] sshd: banne" & 3 [-- Message 3 -- 92 lines, 3367 bytes --]: Subject: [Fail2Ban] sshd: banned 10.0.0.203 from dlp.srv.world Date: Thu, 20 Jun 2024 16:10:51 +0900 From: Fail2Ban <sender = root@dlp.srv.world> To: root@localhost Message-Id: <20240620071051.98B32301E337@dlp.srv.world> Hi, The IP 10.0.0.203 has just been banned by Fail2Ban after 5 attempts against sshd. Here is more information about 10.0.0.203 : ..... ..... |
[4] | If you want to manually add or remove banned hosts, run the following. |
[root@dlp ~]# fail2ban-client status sshd Status for the jail: sshd |- Filter | |- Currently failed: 1 | |- Total failed: 12 | `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd `- Actions |- Currently banned: 1 |- Total banned: 2 `- Banned IP list: 10.0.0.203 # unban [10.0.0.203] [root@dlp ~]# fail2ban-client set sshd unbanip 10.0.0.203 1 fail2ban-client status sshd Status for the jail: sshd |- Filter | |- Currently failed: 1 | |- Total failed: 12 | `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd `- Actions |- Currently banned: 0 |- Total banned: 2 `- Banned IP list: # ban [10.0.0.192/28] [root@dlp ~]# fail2ban-client set sshd banip 10.0.0.192/28 1 fail2ban-client status sshd Status for the jail: sshd |- Filter | |- Currently failed: 1 | |- Total failed: 12 | `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd `- Actions |- Currently banned: 1 |- Total banned: 3 `- Banned IP list: 10.0.0.192/28 # to remove all banned hosts, run like follows [root@dlp ~]# fail2ban-client unban --all |
[5] | [jail.conf] has many predefined services other than SSH, so you can set them as monitoring targets by specifying the definition name. |
[root@dlp ~]# grep '^\[' /etc/fail2ban/jail.conf | tail -n +3 [sshd] [dropbear] [selinux-ssh] [apache-auth] [apache-badbots] [apache-noscript] [apache-overflows] [apache-nohome] [apache-botsearch] [apache-fakegooglebot] [apache-modsecurity] ..... ..... # for example, set up Apache2 Basic authentication [root@dlp ~]# vi /etc/fail2ban/jail.d/apache-auth.conf # create new [apache-auth] enabled = true bantime = 600 findtime = 3m maxretry = 5 action = %(action_mw)s # create new [vsftpd] enabled = true backend = systemd journalmatch = _SYSTEMD_UNIT=vsftpd.service action = %(action_mw)s # create new [postfix-sasl] enabled = true action = %(action_mw)s
[root@dlp ~]#
[root@dlp ~]# systemctl reload fail2ban
fail2ban-client status Status |- Number of jail: 4 `- Jail list: apache-auth, postfix-sasl, sshd, vsftpd # verify settings by failing authentication manually [root@dlp ~]# fail2ban-client status apache-auth Status for the jail: apache-auth |- Filter | |- Currently failed: 0 | |- Total failed: 10 | `- File list: /var/log/httpd/error_log `- Actions |- Currently banned: 1 |- Total banned: 1 `- Banned IP list: 10.0.0.5[root@dlp ~]# fail2ban-client status vsftpd Status for the jail: vsftpd |- Filter | |- Currently failed: 0 | |- Total failed: 5 | `- Journal matches: _SYSTEMD_UNIT=vsftpd.service `- Actions |- Currently banned: 1 |- Total banned: 2 `- Banned IP list: 10.0.0.203 |
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