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(OS X)
(Removing Fail2ban Block)
Line 15: Line 15:
  Chain fail2ban-ssh (1 references)
  Chain fail2ban-SSH (1 references)
  num  target    prot opt source              destination
  num  target    prot opt source              destination
  1    DROP      all  --      anywhere
  1    DROP      all  --      anywhere
Line 32: Line 32:
  iptables -D fail2ban-ssh 2
  iptables -D fail2ban-SSH 2
==Installing Fail2ban==
==Installing Fail2ban==

Latest revision as of 10:40, 7 February 2015


[edit] Fail2ban

We use the package fail2ban on all of our linux machines to help prevent ssh password brute-forcing. This package will block an IP address after a certain number (usually 10) of failed attempts.

[edit] Removing Fail2ban Block

If your address has been accidentally blocked on a server, and you are able to log in and control the server (usually via a different computer) you can remove your banned IP address from iptables.

To unban an IP address manually, it is necessary to know the chain name and the rule number. The following command can be used to acquire this information:


iptables -L -n --line-numbers

The relevant bits are at the end of the output. Here is an example chain with attendant rules:


Chain fail2ban-SSH (1 references)
num  target     prot opt source               destination
1    DROP       all  --       anywhere
2    DROP       all  --          anywhere
3    DROP       all  --  anywhere
4    RETURN     all  --  anywhere             anywhere

In this example, three (3) IP addresses have been banned via the SSH jail (these are the DROP rules).

To unban an IP address, you would run the following command:


iptables -D [chain-name] [line-number]

To unban the IP address (see above), the command would be:


iptables -D fail2ban-SSH 2


[edit] Installing Fail2ban

[edit] OS X

This is an advanced setup, and requires using the terminal to install and modify files.

  1. Download the latest official source tarball:
  2. Unpack by double clicking or command line
  3. $ tar xvfj fail2ban-0.8.14.tar.bz2
  4. Go into the folder and run the following command to install Fail2ban
  5. $ cd fail2ban-0.8.14
    $ sudo python install
  6. Copy the init scipt to the launchdaemon directory
  7. $ sudo cp files/macosx-initd /Library/LaunchDaemons/org.fail2ban.plist
  8. Open the org.fail2ban.plist and delete the first two lines, such that the first line starts with <?xml ...
  9. $ sudo nano /Library/LaunchDaemons/org.fail2ban.plist
  10. Make a log file and give it proper permissions
  11. $ sudo touch /var/log/fail2ban.log
    $ sudo chgrp admin /var/log/fail2ban.log
  12. Add these two lines to /etc/pf.conf
  13. table <fail2ban> persist
    block drop log quick from <fail2ban> to any
  14. Create /etc/fail2ban/jail.local file. Working jail.local file can be downloaded here ###needs url###
  15. Shutdown pf, reload the configuration and restart
  16. $ sudo pfctl -d
    $ sudo pfctl -f /etc/pf.conf
    $ sudo pfctl -e
  17. Edit the following lines in /etc/sshd_config
  18. useDNS no
    PermitRootLogin no
  19. Start the fail2ban client
  20. $ sudo /usr/local/bin/fail2ban-client start
  21. Check your fail2ban logfile in or look at the pf fail2ban table to see if any addresses are blocked
  22. $ sudo pfctl -t fail2ban -T show

[edit] Optional Installs
  1. Install IceFloor
  2. Install Xcode and MacPorts:

add the below line to /opt/local/etc/fail2ban/filters.d/ssh.conf

^%(__prefix_line)s(?:error: PAM: )?unknown user for illegal user .* from <HOST>( via \S+)?\s*$
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