• Checking Fail2ban regex
• Fail2ban high CPU usage

• Fail2ban
• fail2ban is broken in 24.04 Noble

debian11# apt install iptables
debian12# apt install iptables rsyslog

# apt install fail2ban

ubuntu24# ###wget https://launchpad.net/ubuntu/+source/fail2ban/1.1.0-1/+build/28291332/+files/fail2ban_1.1.0-1_all.deb
ubuntu24# ###dpkg -i fail2ban_1.1.0-1_all.deb 

# cat /etc/fail2ban/jail.conf

# ls /etc/fail2ban/jail.d/

# cat /etc/fail2ban/jail.d/defaults-debian.conf

# cat /etc/fail2ban/filter.d/sshd.conf

# cat /etc/fail2ban/filter.d/asterisk.conf

# cat /etc/fail2ban/jail.local

[sshd]
maxretry = 6
#port = 2222
#ignoreip = 192.168.X.0/24 192.168.100+X.0/24

[asterisk]
enabled = true
maxretry = 3
#bantime = 30d
#action = iptables-allports[blocktype=DROP]
#action = route[blocktype=blackhole]

#https://github.com/fail2ban/fail2ban/discussions/3836|Asterisk 20.6 on Ubuntu 24.04: Fail2Ban not working
#backend = auto
#logpath  = /var/log/asterisk/messages.log

# service fail2ban reload

# tail -f /var/log/fail2ban.log

# fail2ban-client status

# fail2ban-client status asterisk

# iptables-save
# nft list ruleset

# fail2ban-client set asterisk unbanip 172.16.1.150

# tail -f /var/log/fail2ban.log

• Резервное копирование конфигурации

# cat /etc/fail2ban/jail.d/cisco-change-config.conf

[cisco-change-config]
enabled  = true
maxretry = 1
bantime  = 30
filter   = cisco-change-config
logpath  = /var/log/cisco.log
action   = cisco-backup-config

# cat /etc/fail2ban/filter.d/cisco-change-config.conf

[Definition]

failregex = <HOST>.*Configured from.*

# cat /etc/fail2ban/action.d/cisco-backup-config.conf

[Definition]

actionban = /usr/bin/sshpass -p cisco /usr/bin/scp <ip>:running-config /srv/tftp/<ip>-running-config
            cd /srv/tftp/
            /usr/bin/git add *
            /usr/bin/git --no-optional-locks status | grep 'modified\|deleted\|new file' | /usr/bin/git commit -a -F -

• frankiejol/snortban
• Сервис SNORT Копирование alert_unified2 в syslog

# cat /etc/fail2ban/jail.d/snort_jail.conf

[snort]
enabled     = true
bantime     = 300
filter      = snort_filter
maxretry    = 3
logpath     = /var/log/auth.log
#action      = mail-admin
#action      = iptables-allports
#action      = iptables-allports-forward
#action      = cisco-acl

# cat /etc/fail2ban/filter.d/snort_filter.conf

[Definition]

failregex = .*snort.*Priority: 1.*} <HOST>.*
#        .*snort.*Priority: 2.*} <HOST>.*

#failregex = .*Original Client IP: <HOST>.*

# cat /etc/fail2ban/action.d/mail-admin.conf

[Definition]

actionban = printf %%b "Hi,\n
            Ban this <ip>
            Regards,\n
            Fail2Ban"|mail -s "[Fail2Ban] Ban <name> <ip>" <dest>

actionunban = printf %%b "Hi,\n
            Unban this <ip>
            Regards,\n
            Fail2Ban"|mail -s "[Fail2Ban] Unban <name> <ip>" <dest>

[Init]

name = mail-admin

dest = student

• Запуск и отладка

# cp /etc/fail2ban/action.d/iptables-allports.conf /etc/fail2ban/action.d/iptables-allports-forward.conf

# cat /etc/fail2ban/action.d/iptables-allports-forward.conf

...
before = iptables-common-forward.conf
...

# cp /etc/fail2ban/action.d/iptables-common.conf /etc/fail2ban/action.d/iptables-common-forward.conf

# cat /etc/fail2ban/action.d/iptables-common-forward.conf

...
chain = FORWARD 
...

• Запуск и отладка

server# rsh router show access-lists

# cat /root/cisco-acl-deny.sh

#!/bin/sh

fail2ban-client status snort | grep Banned | cut -d':' -f2 | tr -s ' ' | tr " " "\n" |
while read ip
do
        test -z "$ip" && continue
        echo " deny ip host $ip any"
done

# cat /root/cisco-acl-permit.txt

 permit tcp any host 192.168.X.10 eq 80
 permit tcp any host 192.168.X.10 eq 22
 permit icmp any 192.168.0.0 0.0.255.255
 permit ip any host 172.16.1.X
 permit udp any any
 permit tcp any any established
 deny   ip any any ! log
end

# cat /root/cisco-change-firewall.sh

#!/bin/sh

cat > /srv/tftp/firewall.acl <<EOF
no ip access-list extended ACL_FIREWALL
ip access-list extended ACL_FIREWALL
EOF

/root/cisco-acl-deny.sh >> /srv/tftp/firewall.acl

cat /root/cisco-acl-permit.txt >> /srv/tftp/firewall.acl

#/usr/bin/rcp /srv/tftp/firewall.acl router:running-config
#/usr/bin/snmpset -c write -v2c router .1.3.6.1.4.1.9.2.1.53.192.168.X.10 string "firewall.acl"

# cat /etc/fail2ban/action.d/cisco-acl.conf

[Definition]

actionban = /root/cisco-change-firewall.sh

actionunban = /root/cisco-change-firewall.sh
# if atack from DNS)
#actionunban = echo /root/cisco-change-firewall.sh | at now + 1 min

• Запуск и отладка

# fail2ban-regex /var/log/tmp_file.log /etc/fail2ban/filter.d/tmp_file_filter.conf

# cat action.d/tmp_file_action.conf

[Definition]

actionban = echo "`date` f2ban detect ip: <ip>" >> /tmp/file_action.log

• Asterisk 11.5 + Fail2Ban

# less filter.d/asterisk.conf

[INCLUDES]

# Read common prefixes. If any customizations available -- read them from
# common.local
before = common.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 = NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - Wrong password
            NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - No matching peer found
            NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - No matching peer found
            NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - Username/auth name mismatch
            NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - Device does not match ACL
            NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - Peer is not supposed to register
            NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - ACL error (permit/deny)
            NOTICE.* .*: Registration from '.*' failed for '<HOST>:.*' - Device does not match ACL
            NOTICE.* .*: Registration from '\".*\".*' failed for '<HOST>:.*' - No matching peer found
            NOTICE.* .*: Registration from '\".*\".*' failed for '<HOST>:.*' - Wrong password
            NOTICE.* <HOST> failed to authenticate as '.*'$
            NOTICE.* .*: No registration for peer '.*' \(from <HOST>\)
            NOTICE.* .*: Host <HOST> failed MD5 authentication for '.*' (.*)
            NOTICE.* .*: Failed to authenticate user .*@<HOST>.*
            NOTICE.* .*: <HOST> failed to authenticate as '.*'
            NOTICE.* .*: <HOST> tried  to authenticate with nonexistent user '.*'
            VERBOSE.*SIP/<HOST>-.*Received incoming SIP connection from unknown peer
        NOTICE.* .*: Sending fake auth rejection for device.* \(<HOST>:.*\)
        NOTICE.* .*: Sending fake auth rejection for device .*\<sip:.*\@.*\>;tag=.* \(<HOST>:.*\)
        NOTICE.* .*: Failed to authenticate device .*\<sip:.*\@.*\>;tag=.* \(<HOST>:.*\)
            NOTICE.* .*: Sending fake auth rejection for device.* \(<HOST>:.*\)
            NOTICE.* .*: Sending fake auth rejection for device .*\;tag=.* \(<HOST>:.*\)


# Option:  ignoreregex
# Notes.:  regex to ignore. If this regex matches, the line is ignored.
# Values:  TEXT
#
ignoreregex =

failregex = SECURITY.* SecurityEvent="FailedACL".*RemoteAddress=".+?/.+?/<HOST>/.+?".*
            SECURITY.* SecurityEvent="InvalidAccountID".*RemoteAddress=".+?/.+?/<HOST>/.+?".*
            SECURITY.* SecurityEvent="ChallengeResponseFailed".*RemoteAddress=".+?/.+?/<HOST>/.+?".*
            SECURITY.* SecurityEvent="InvalidPassword".*RemoteAddress=".+?/.+?/<HOST>/.+?".*