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This is an easy and small script to allow customized drop rules on your iptables Firewall to protect against intruders on your network.
The script follows the same approach then Syslog to Firewall but runs on Linux together with iptables and psad.
Finally this goes into the direction of a IPS


Psad2ipt has been tested on Linux Debian 8 (Jessie) but should run on any other recent Linux Distribution too.


  • Provides a easy IPS based on OSS for nuts!
  • It runs on it's own, no additional server software is required (such as LAMP), only Perl with a few additional Modules is needed.
  • Sqlite3 is used (that's based on a flat file) to allow to cope a large activity with psad2ipt.
  • Dynamic ramp up the drop time, an intruder get first blocked by default with 15, then 30, 60, 120 and so on minutes on every occurrence of an event.
  • Tight ip address checking to avoid false blockings, psad2ipt does not want to get blamed.
  • Optional reporting into a Splunk server.
  • Blame protection - never block internal or known customer addresses.

Setup and Operation description

Pad2ipt runs on it's own iptables chain to add or remove malicious ip addresses which has been identified by psad.
The iptables chain must be present at runtime [abort if not] so creating the Psad2ipt chain is a essential step to do first.
If psad2ipt get's called by psad then it takes immediatly action and blocks the ip by adding a iptables rule into it previous assigned chain.
The rule is using the state connection module to identify incoming packages only and requires the outside interface name to specify the direction,
this way it should be a save drop rule to avoid false blockings. We also offer a whitelist function to prevent wrong data assignment.
However, psad2ipt will never add private ip addresses into it's chain, even if specified to do so.


Download and extract the archive to /usr/local/psad2ipt, a different path is possible by setup the configuration file.

List of files

  • - Script
  • psad2ipt.xml - Configuration
  • psad2ipt.db - Database

Install Perl Modules

  • This will work with Debian
apt-get install libipc-run-perl
apt-get install libproc-processtable-perl
apt-get install libdbi-perl
apt-get install libdbd-sqlite3-perl 
cpan Net::Syslog


Setup psad2ipt

  • Edit psad2ipt.xml
XML Child Element XML Attribute Value



Chain Name to be used with psad2ipt, the default is P2I


Maximum events with a single IP addrress,
this is a counter which counts until the amount has been reached before blocking this ip address.
The default is 1


Maximum days of events which is keeped within the database, older records will be deleted


Number of Days where psad2ipt looks behind to get get amount of events for the specified ip address
This values is used when running psad2ipt with the options -A and -C


Used for flooding prevention, it is the maximum number of rules allowed within the psad2ipt chain


This is the startup amount of mintes which psad2ipt will use when it's get called with the option -A
The unit is Minutes
The default is 15 Minutes
The amount will dynamically increase on every event, first 15, then 30, 60, 120 and so on


If set to 1 then psad2ipt will write into syslog to localhost using UDP 514,
Note that this needs to be setup within the syslog daemon configuration before for doing this


Path to DB File, this is needed to be used with option -c


If UseSyslog equals 0 then the specified path is used to wrtie the psa2ipt log files


Path to be used for reading whitelist files


Required: Name of outsite interface name, for exampe eth0, this value has no default!


IP address of the splunk server where psad2ipt is sending messages to UDP 514

Setup iptables

To setup iptable it is essential to define the rule, example for the default rule 'P2I'

/sbin/iptables -N P2I

Note that the chain will have no affect unless it has been assigned to the INPUT or FORWARD rule of iptables.
Assigning the chain:

/sbin/iptables -A INPUT -j P2I
/sbin/iptables -A FORWARD -j P2I
  • Note that the assignment must be placed after the rule creation and before the default drop chain/rule

Running psad2ipt

psad2ipt can be applied with the following option:

  • Check the inventory, delete expired addresses from the chain, use the configuration option to allow this command to be allowed from everywhere else then our home directory
#/psad2ipt -C -c /usr/local/psad2ipt/psad2ipt.xml
  • Check the inventory, delete expired addresses from the chain
/usr/local/psad2ipt #./psad2ipt -C
  • Add the sample address ( to the specified chain (P2I), this is done immediately.
/usr/local/psad2ipt #./psad2ipt -A
  • List the database records
/usr/local/psad2ipt #./psad2ipt -l
  • Delete a single ip address from the environment
/usr/local/psad2ipt #./psad2ipt -D
  • Flush the database
/usr/local/psad2ipt #./psad2ipt -F


  • Example rule in chain P21
[email protected]:/usr/local/psad2ipt# iptables -L P2I -n
Chain P2I (1 references)
target     prot opt source               destination
DROP       all  --               state NEW /* Dynamic rule by P2I at 2016-02-19 19:16:02 */