Overview
Install and configure Fail2Ban to block attacking hosts using a null route or blackhole routes.
- PRO:
- – Works on all kernel versions and as no compatibility problems (back to debian lenny and WAY further).
- – It’s FAST for very large numbers of blocked ips.
- – It’s FAST because it Blocks traffic before it enters common iptables chains used for filtering.
- – It’s per host, ideal as action against ssh password bruteforcing to block further attack attempts.
- – No additional software required beside iproute/iproute2
- CON:
- – Blocking is per IP and NOT per service, but ideal as action against bruteforcing hosts.
Prerequisite:
It is required the OIP configuration must be done before configuring Fail2Ban service.
For a Single-Server Setup:
If you are running nginx on the same node as the mailstore, you will need to add both 127.0.0.1 and the real IP address of that node:
su - zimbra
zmprov mcf +zimbraMailTrustedIP 127.0.0.1 +zimbraMailTrustedIP {IP of Server}
zmcontrol restart
For a Multi-Server Setup:
su - zimbra
zmprov mcf +zimbraHttpThrottleSafeIPs {IP of Mailbox-1}
zmprov mcf +zimbraHttpThrottleSafeIPs {IP of Mailbox-2}
zmprov mcf +zimbraMailTrustedIP {IP of Proxy-1}
zmprov mcf +zimbraMailTrustedIP {IP of Proxy-2}
zmcontrol restart
Installation and Configuration of Fail2Ban:
1) Install Fail2Ban Package
- On RHEL/CentOS 7/8:
yum install epel-release -y yum install fail2ban -y
- On Ubuntu 16/18:
apt-get clean all ; apt-get update apt-get install fail2ban -y
2) Create a file “/etc/fail2ban/jail.local” and it will override the default conf file “/etc/fail2ban/jail.conf”.
Add the local IP address of the Zimbra server in “ignoreip =”. You can also add other IP addresses to ignore from Fail2Ban checking.
On a multi-server setup, add all server’s IP in ignoreip list.
vim /etc/fail2ban/jail.local
[DEFAULT] # "ignoreip" can be a list of IP addresses, CIDR masks or DNS hosts. Fail2ban will not ban a host which matches an address in this list. # Several addresses can be defined using space (and/or comma) separator. #ignoreip = 127.0.0.1/8 ::1 10.137.26.29/32 ignoreip = 127.0.0.1/8 "IP-ADDRESS-OF-ZIMBRA-SERVER/32" banaction = route # A host is banned if it has generated "maxretry" during the last "findtime" seconds. # 10 minute (in seconds) #findtime = 600 # "bantime" is the number of seconds that a host is banned. # 10 hour (in seconds) #bantime = 3600 # "maxretry" is the number of failures before a host get banned. #maxretry = 5
| ignoreip: | This parameter identifies IP address that should be ignored by the banning system. By default, this is just set to ignore traffic coming from the machine itself, which is a pretty good setting to have. |
| banaction: | This sets the action that will be used when the threshold is reached. There is actually the name of a file located in /etc/fail2ban/action.d/ which calls the configured action using the .conf file.Here we configured route which calls route.conf to handle the routing table manipulation to ban an IP address. |
| findtime: | This parameter sets the window that fail2ban will pay attention to when looking for repeated failed authentication attempts. The default is set to 600 seconds (10 minutes again), which means that the software will count the number of failed attempts in the last 10 minutes. |
| bantime: | This parameter sets the length of a ban, in seconds. The default is 600 seconds, or 10 minutes. |
| maxretry: | This sets the number of failed attempts that will be tolerated within the findtime window before a ban is instituted. |
3) Create a jail file for Zimbra services.
vim /etc/fail2ban/jail.d/zimbra.local
[zimbra-smtp] enabled = true filter = zimbra-smtp port = 25,465,587 logpath = /var/log/zimbra.log maxretry = 3 findtime = 600 bantime = 3600 [zimbra-webmail] enabled = true filter = zimbra-webmail port = 80,443 logpath = /opt/zimbra/log/mailbox.log maxretry = 3 findtime = 600 bantime = 3600 [zimbra-admin] enabled = true filter = zimbra-admin port = 7071,9071 logpath = /opt/zimbra/log/mailbox.log maxretry = 3 findtime = 600 bantime = 3600
4) [Optional]
If you want to apply Fail2Ban for SSH then create jail file sshd.local.
(No need to create filter rules for SSH, Fail2ban by default shipped with filter rules for SSH)
On Ubuntu systems, SSH jail is by default enabled within the jail file “/etc/fail2ban/jail.d/defaults-debian.conf”.
vim /etc/fail2ban/jail.d/sshd.local
[sshd] enabled = true port = 22 maxretry = 3 findtime = 600 bantime = 3600
5) Create filters for Zimbra services.
vim /etc/fail2ban/filter.d/zimbra-webmail.conf
[Definition]
#
failregex = \[oip=<HOST>;.* SoapEngine - handler exception: authentication failed for .*, account not found$
INFO .*;oip=<HOST>;.* SoapEngine - handler exception: authentication failed for .*, invalid password$
ignoreregex =
vim /etc/fail2ban/filter.d/zimbra-smtp.conf
[Definition]
#
failregex = postfix\/submission\/smtpd\[\d+\]: warning: .*\[<HOST>\]: SASL \w+ authentication failed: authentication failure$
postfix\/smtps\/smtpd\[\d+\]: warning: .*\[<HOST>\]: SASL \w+ authentication failed: authentication failure$
ignoreregex =
vim /etc/fail2ban/filter.d/zimbra-admin.conf
[Definition]
#
failregex = INFO .*;ip=<HOST>;.* SoapEngine - handler exception: authentication failed for .*, invalid password$
INFO .*ip=<HOST>;.* SoapEngine - handler exception: authentication failed for .*, account not found$
ignoreregex =
6) Restart the Fail2ban service and enable it to start after system reboot.
systemctl restart fail2ban systemctl status fail2ban systemctl enable fail2ban
7) Check the status of the Fail2Ban jails.
fail2ban-client status
The result should be similar to this:
Example:
[root@centos8 ~]# fail2ban-client status Status |- Number of jail: 4 `- Jail list: sshd, zimbra-admin, zimbra-smtp, zimbra-webmail [root@centos8 ~]#
[root@centos8 ~]# fail2ban-client status sshd Status for the jail: sshd |- Filter | |- Currently failed: 0 | |- Total failed: 14 | `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd `- Actions |- Currently banned: 1 |- Total banned: 2 `- Banned IP list: 10.137.26.29
8) Check banned IP in routing table.
ip r
route -n
The result should be similar to this:
Example:
[root@centos8 ~]# ip r default via 10.0.10.1 dev ens3 10.0.10.0/24 dev ens3 proto kernel scope link src 10.0.10.67 unreachable 10.137.26.29 [root@centos8 ~]#
[root@centos8 ~]# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 10.0.10.1 0.0.0.0 UG 0 0 0 ens3 10.0.10.0 0.0.0.0 255.255.255.0 U 0 0 0 ens3 10.137.26.29 - 255.255.255.255 !H 0 - 0 - [root@centos8 ~]#
9) Ban and unban an IP manually.
- Ban an IP address.
fail2ban-client set "Jail-Name" banip "IP-Address"
Example:
fail2ban-client set sshd banip 10.137.26.29
- Unban an IP address.
fail2ban-client set "Jail-Name" unbanip "Banned IP-Address"
Example:
[root@centos8 ~]# fail2ban-client set sshd unbanip 10.137.26.29
