Fail2Ban
Basic fail2ban installation and setup
Contents |
Installation
Install EPEL Repos
- For CentOS 5 i386:
# rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-4.noarch.rpm
- For CentOS 4:
# rpm -Uvh http://download.fedora.redhat.com/pub/epel/4/i386/epel-release-4-10.noarch.rpm
Instal fail2ban:
# yum install fail2ban
Setup
To work with Qmail/vpopmail, a filter and jail should be defined.
- Create a filter
# vi /etc/fail2ban/filter.d/password-fail.conf
[Definition]
#Looks for failed password logins to SMTP
failregex = vchkpw-smtp: password fail ([^)]*) [^@]*@[^:]*:<HOST>
ignoreregex =
# vi /etc/fail2ban/filter.d/username-notfound.conf
[Definition]
# Option: failregex
# Notes.: regex to match the password failures messages in the logfile.
# The host must be matched by a group named "host". The tag "<HOST>" can
# be used for standard IP/hostname matching and is only an alias for
# (?:::f{4,6}:)?(?P<host>\S+)
# Values: TEXT
failregex = vchkpw-smtp: vpopmail user not found .*:<HOST>
# Option: ignoreregex
# Notes.: regex to ignore. If this regex matches, the line is ignored.
# Values: TEXT
ignoreregex =
- Create a jail (add these lines)
# vi /etc/fail2ban/jail.conf
[password-fail]
enabled = true
filter = password-fail
action = iptables[name=SMTP, port=smtp, protocol=tcp]
logpath = /var/log/maillog
maxretry = 3
bantime = 86400
findtime = 3600
[username-notfound]
enable = true
filter = username-notfound
action = iptables[name=SMTP, port=smtp, protocol=tcp]
logpath = /var/log/maillog
maxretry = 3
bantime = 86400
findtime = 3600
- Test the filter file (Returns something like this, with n matches for the regex or 0 if no matches):
# fail2ban-regex /var/log/maillog /etc/fail2ban/filter.d/password-fail.conf
Failregex
|- Regular expressions:
| [1] vchkpw-smtp: password fail ([^)]*) [^@]*@[^:]*:<HOST>
|
`- Number of matches:
[1] 123 match(es)
- Reload config:
# fail2ban-client stop
# fail2ban-client start
- Check the status of a jail:
# fail2ban-client status password-fail
Status for the jail: password-fail
|- filter
| |- File list: /var/log/maillog
| |- Currently failed: 7
| `- Total failed: 225
`- action
|- Currently banned: 109
| `- IP list: 200.207.49.13 84.79.73.123 187.35.209.243 (...) 187.6.106.201 187.63.80.134 187.52.195.234 187.4.200.17
`- Total banned: 109
NOTE: Once its starts running and the logs have matching strings, it will create iptables rules dropping that IP. But when fail2ban reload and/or iptables restart and/or rebooting and/or the weekly logrotate, those rules are gone. bye bye! So what to do?
- Before changes, write existing iptables rules to file
# service iptables save
- And after any change load the saved set of rules
# service iptables restart
- Tune fail2ban to write IPs to /etc/fail2ban/ip.deny
Basic admin stuff
- Check banned IPs:
- from fail2ban:
# fail2ban-client status vpopmail-fail
- from current iptables rules:
# iptables -L -nv
- To see IPs that fail2ban is saving for the next reload:
# cat /etc/fail2ban/ip.deny
- How to unblock an IP:
- Delete it from the current iptables rules:
# iptables -D fail2ban-SMTP -s 11.22.33.44 -j DROP
- Remove it from /etc/fail2ban/ip.deny (maybe listed several times).
- Remove it from /etc/sysconfig/iptables (maybe listed several times).
References
[0] http://www.mail-archive.com/qmailtoaster-list@qmailtoaster.com/msg30514.html
[1] http://www.mail-archive.com/qmailtoaster-list@qmailtoaster.com/msg30551.html
[2] http://fedoraproject.org/wiki/EPEL/FAQ#howtouse
[3] http://n8wood.wordpress.com/2009/06/22/fail2ban-permanent-ssh-bans/
[4] fail2ban homepage: http://www.fail2ban.org