Denyhosts

Automated host blocking from SSH brute force attacks

Description

DenyHosts is a utility developed by Phil Schwartz and maintained by a number of developers which aims to thwart sshd (ssh server) brute force attacks.

Code Quality Rank: L3

Programming language: Python

License: GNU General Public License v2.0 only

Tags: Security    

Latest version: v3.1

README

DenyHosts

DenyHosts is a utility developed by Phil Schwartz and maintained by a number of developers which aims to thwart sshd (ssh server) brute force attacks.

Please refer to https://github.com/denyhosts/denyhosts for more information.

Installation

Requirements

The DenyHosts software depends on the "ipaddr" Python module, which is available in most Linux and BSD repositories.

Source Distribution

If you downloaded the source distribution file (DenyHosts-#.#-tar.gz) then:

$ tar zxvf DenyHosts-3.1.tar.gz 

$ cd denyhosts

as root:

# python setup.py install

This will install the DenyHosts modules into python's site-packages directory.

Binary Distribution (rpm, deb, etc)

It is assumed that you are familiar with installing a binary package on your particular operating system. If you are unsure how to do this, you may wish to install from source instead.

All Distributions

DenyHosts requires that a configuration file be created before it can function. The sample configuration file denyhosts.conf contains most of the possible settings and should be copied and then edited as such:

# cp denyhosts.conf /etc

# nano /etc/denyhosts.conf

(nano is a simple text editor. Feel free to use your own favourite text editor such as emacs, vi, etc)

The sample configuration file contains informational comments that should help you quickly configure DenyHosts. After you have edited your configuration file, save it.

Next, if you intend to run DenyHosts in daemon mode (recommended) copy the sample daemon-control.dist script as such:

# cp daemon-control-dist daemon-control

Edit the daemon-control file. You should only need to edit this section near the top:

###############################################
#### Edit these to suit your configuration ####
###############################################

DENYHOSTS_BIN   = "/usr/bin/denyhosts.py"
DENYHOSTS_LOCK  = "/var/lock/subsys/denyhosts"
DENYHOSTS_CFG   = "/etc/denyhosts.conf"

These defaults should be reasonable for many systems. You should customize these settings to match your particular system.

Once you have edited the configuration and daemon control files make sure that the daemon control script it executable (by root).

# chown root daemon-control

# chmod 700 daemon-control

Starting DenyHosts Manually

Assuming you have configured DenyHosts to run as a daemon, you can use the daemon-control script to control it:

# daemon-control start

You should refer to the daemon log (typically /var/log/denyhosts) to ensure that DenyHosts is running successfully. If you notice any problems you may wish to consult the FAQ at http://www.denyhosts.net/faq.html

If you wish to run DenyHosts from cron rather than as a daemon, please refer to the FAQ.

Another way to start DenyHosts manually is to run it from the command line, usually supply a few common parameters. Usually, when running DenyHosts from the command line (or from the /etc/rc.local script) we can launch the program by running

 # python /usr/local/bin/denyhosts --config /etc/denyhosts.conf --daemon

The above command launches DenyHosts and runs it in the background. DenyHosts will use the /etc/denyhosts.conf configuration file to dictate its behavour.

Starting DenyHosts Automatically

Method 1 (preferred)

Create a symbolic link from /etc/init.d such as:

# cd /etc/init.d
# ln -s /usr/share/denyhosts/daemon-control denyhosts

If you have chkconfig installed you can then use it to ensure that DenyHosts runs at boot time:

# chkconfig --add denyhosts

If you do not have chkconfig (or similar) installed you can either manually create the symlinks in /etc/rc2.d, /etc/rc3.d, /etc/rc5.d but that is beyond the scope of this document.

Method 2

Add an entry into the /etc/rc.local file:

/usr/share/denyhosts/daemon-control start