Fail2ban
Fail2ban scans log files like /var/log/pwdfail
or /var/log/apache/error_log
and bans IP that makes too many password failures. It updates firewall rules to reject the IP address.
Contents
Installation
First, install python2-pyinotify so that Fail2ban can detect modification to the log files:
# pacman -S python2-pyinotify
Then, install fail2ban:
# pacman -S fail2ban
If you want Fail2ban to send an email when someone has been banned, you have to configure SSMTP (for example). You will also have to install whois to get some information about the attacker.
# pacman -S whois
systemd
Use the service unit fail2ban.service, refer to systemd for instructions.
syslog-ng
. This is because journald
does not use /var/log/auth.log
which is parsed by Fail2ban.Hardening
Currently, fail2ban requires to run as root, therefore you may wish to consider some additional hardening on the process with systemd. Ref:systemd for Administrators, Part XII
Capabilities
For added security consider limiting fail2ban capabilities by adding CapabilityBoundingSet under [Service]
section of the systemd service file, e.g.:
CapabilityBoundingSet=CAP_DAC_READ_SEARCH CAP_NET_ADMIN CAP_NET_RAW
In the example above, CAP_DAC_READ_SEARCH will allow fail2ban full read access, and CAP_NET_ADMIN and CAP_NET_RAW allow setting of firewall rules with iptables. Additional capabilities may be required, depending on your fail2ban configuration. See man capabilities
for more info.
Filesystem Access
Also considering limiting file system read and write access, by using ReadOnlyDirectories and ReadWriteDirectories, again under the under [Service]
section. For example:
ReadOnlyDirectories=/ ReadWriteDirectories=/var/run/fail2ban /var/spool/postfix/maildrop
In the example above, this limits the file system to read-only, except for /var/run/fail2ban
for pid and socket files, and /var/spool/postfix/maildrop
for postfix sendmail. Again, this will be dependent on you system configuration and fail2ban configuration. Note that adding /var/log
is necessary if you want fail2ban to log its activity.
SSH jail
Edit /etc/fail2ban/jail.conf
and modify the ssh-iptables section to enable it and configure the action.
If your firewall is iptables:
[ssh-iptables] enabled = true filter = sshd action = iptables[name=SSH, port=ssh, protocol=tcp] sendmail-whois[name=SSH, dest=your@mail.org, sender=fail2ban@mail.com] logpath = /var/log/auth.log maxretry = 5
If your firewall is shorewall:
[ssh-shorewall] enabled = true filter = sshd action = shorewall sendmail-whois[name=SSH, dest=your@mail.org, sender=fail2ban@mail.com] logpath = /var/log/auth.log maxretry = 5
BLACKLISTNEWONLY
to No
in /etc/shorewall/shorewall.conf
otherwise the rule added to ban an IP address will affect only new connections.Also do not forget to add/change:
LogLevel VERBOSE
in your /etc/ssh/sshd_config
. Else, password failures are not logged correctly.