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Asif Bacchus
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README.md
42
README.md
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This is a basic set up for Fail2Ban on an system that is directly exposed to the
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internet (i.e. not behind a separate firewall).
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**This set-up assumes you are using UFW as your firewall front-end and it's
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**This set-up assumes you are using UFW as your firewall front-end and it is
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working correctly.**
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In addition to the standard SSHd jail, a separate jail that monitors UFW BLOCK
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@ -54,7 +54,7 @@ newer version from the source at github.
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```
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- Let's go ahead and start the service to make sure it doesn't run into any
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problems. You shouldn't see any errors reported and should have a pleasant
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problems. You should not see any errors reported and should have a pleasant
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'green dot' showing up.
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```Bash
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@ -79,13 +79,12 @@ updates.
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### /etc/fail2ban/fail2ban.conf
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I recommend reviewing your the following settings at a minimum for any
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deployment:
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I recommend reviewing the following settings at a minimum for any deployment:
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#### loglevel
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This sets the verbosity of the log output from F2B. The default setting of INFO
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is appropriate for most installs but, you should specify it anyways so you have
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any easy place to change it if you need to do so.
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an easy place to change it if you need to do so.
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```Ini
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loglevel = INFO
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@ -113,7 +112,7 @@ dbpurgeage = 604800
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### /etc/fail2ban/jail.local
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This file overrides the defaults applied to all jail configurations used by F2B.
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This file customizes the defaults applied to all jail configurations used by F2B.
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This sets things like the default amount of time a system is banned, what
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actions should be used for banning systems and whether or not you get email
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notifications, etc.
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@ -122,9 +121,10 @@ notifications, etc.
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This setting tells F2B which IP addresses/ranges/hostnames should **never** be
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banned. In general, this should be the localhost only. However, if you connect
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by remote using a particular machine, you might want to exempt it from any
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possible bans also. You can specify more than one entry by separating them with
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a space or comma. In this case, I've added the IP4 and IP6 defintions for localhost.
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by remote using a particular machine, you might also want to exempt it from any
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possible bans. You can specify more than one entry by separating them with a
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space or comma. In this case, I've added the IP4 and IP6 defintions for
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localhost.
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```Ini
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ignoreip = 127.0.0.1/8 ::1
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@ -173,12 +173,12 @@ sender = thismachine@domain.tld
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mta = sendmail
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```
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The '*mta*' field is very likely correct for your system, but if you are using a
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The '*mta*' field is very likely correct for your system but, if you are using a
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different MTA, you'll want to specify that here.
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##### Shortcuts
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This is where you tell F2B what exactly to do when it finds a reason to ban a
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This is where you tell F2B exactly what to do when it finds a reason to ban a
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system based on the jail configuration. Again, individual jails can override
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these settings. The settings are defined backwards in this file, so I'll take a
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second to explain.
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@ -193,7 +193,9 @@ banned.
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Within '*action*' is '*banaction*' which is a link over to a specific
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configuration file telling F2B what to do on the system to enforce the ban. In
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this setup, we direct F2B to look at the ufw.conf file to see how to modify
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UFW's rules so it drops packets from the offending system. Details on that file are found later in this document.
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UFW's rules so it drops packets from the offending system. [Details on that
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file are found later in this
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document](#The-action-file-(/etc/fail2ban/action.d/ufw.conf)).
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The general setup as described above is as follows:
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@ -210,9 +212,9 @@ preference since it allows for each jail to be contained in it's own
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configuration file which makes debugging and maintaining them much easier.
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### sshd (/etc/fail2ban/jail.d/ssh.conf)
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I usually just define a jail for *sshd* which is the SSH server. You can add
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additional SSH jails as you wish to this file, but I keep it pretty simple. One
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note, I run my SSH server on a non-standard port, so be sure you fill in the
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I usually just define a basic jail for *sshd* which is the SSH server. You can
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add additional SSH jails as you wish to this file, but I keep it pretty simple.
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One note, I run my SSH server on a non-standard port, so be sure you fill in the
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correct port for your environment such as my example below of port 222:
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```Ini
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@ -235,7 +237,7 @@ logpath = /path/to/your/log.file
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### UFW port probing
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This is probably the what you are really looking for in this entire set-up. We
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This is probably the part you are really looking for in this entire set-up. We
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will create a custom jail that monitors UFW's logs for any mention of *[UFW
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BLOCK]* and then proceeds to ban those systems attempting to connect to blocked
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ports as per your timeframe settings. I've commented the ufw-probe file but
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@ -281,7 +283,7 @@ it's the UFW log file which is, by default, located at */var/log/ufw.log*. If
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you've changed this, then update the '*logpath*' parameter. We also need to
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tell it what filter to use when parsing the file, in this case, it's a filter
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I've called 'ufw-probe' (change this if you change the filename) which is
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located at */etc/fail2ban/filter.d/ufw-probe.conf* [details here](#The-UFW-filter-regex-(/etc/fail2ban/filter.d/ufw-probe.conf)). Finally, we
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located at */etc/fail2ban/filter.d/ufw-probe.conf* [(details here)](#The-UFW-filter-regex-(/etc/fail2ban/filter.d/ufw-probe.conf)). Finally, we
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tell F2B to enable this jail.
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```Ini
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@ -320,7 +322,7 @@ have only changed the '*blocktype*' from it's default (reject) to *deny*.
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blocktype = deny
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```
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For example, the important part of '*actionban*' works like this:
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The important part of '*actionban*' works like this:
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```PHP
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ufw insert <insertpos> <blocktype> from <ip> to <destination>
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@ -337,7 +339,7 @@ application =
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```
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So, this rule adds a new rule (*insert*) at position 1 (*insertpos*) which
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denies (*blocktype*) packets from the offending system's IP (*ip*) destinend for
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denies (*blocktype*) packets from the offending system's IP (*ip*) destined for
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any address (which obviously includes this system). Importantly, each rule is
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added at *position 1* which means they have priority over any other
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otherwise defined (i.e. allowed) traffic.
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@ -353,6 +355,6 @@ automatically for whatever timeframe you specify and then remove that block. So
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you don't have to maintain IP block/allow lists manually anymore!
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I hope this helps you in dealing with your server getting bombarded by
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irritating scanning-bots. As always, check out my block at
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irritating scanning-bots. As always, check out my blog at
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https://mytechiethoughts.com for more solutions like this and feel free to
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contribute comments, suggestions and improvements!
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