Tag: IDS

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One of the better features of Palo Alto’s PAN-OS is the ability to define dynamic block lists as firewall objects. These objects can poll a HTTP/HTTPS source for a list of IPs or URLs which can then be acted upon by firewall policies. There are a number of publicly available IP lists and threat intelligence feeds that can be consumed by these objects on the Palo Alto firewall but generating IP lists from internal sources, such as IDS/IPS can be cumbersome. Depending on the type of threats you encounter, it may be beneficial to block IP addresses or URLs picked up by your IDS systems.

To solve this problem I wrote a python script to manage a dymamic IP list that can be consumed by Palo Alto. This script can be run at the command line to generate a list of IP addresses. Use on a SIEM to dynamically block threats that match IDS/IPS rules. All data is stored in a local JSON file and an IP list is outputted to a text file at the designated location. JSON stores information regarding current, historical and excluded IPs. The script logs to a syslog file and to the terminal if verbose is enabled.

I wanted a relatively low maintenance solution and the initial use case for the was to temporarily block reconnaissance traffic such as port scanning. Given this, I used a penalty system to increment the time an IP is blocked each time the IP is seen. Of course, you could utilize the script to block the IP indefinitely also.

You can find the tool on Github at https://github.com/derricksmith/siem/tree/master/av2pa and the command usage is below. If you find this script useful, please drop me a comment below or on Github.



-a, –action           Define the action [add,remove,exclude,clear]

-v, –verbose        Output to terminal

-i, –ip                  IP address (required when action = add,remove,exclude)

-p, –penalty        Penalty for IP address



Add an IP address to the block list. If no penalty is defined the penalty is incremented each time the IP address is added until it reaches 16(indefinite).


Remove an IP address from the block list. Removes the IP from the current, history and exclude dictionaries.


Add an IP to the exclude list. Excluded IPs will not be processed.


Removes all IPs from the current, history and exclude dictionaries.


Cycles the blocklist and checks IPs and Penalty times. If penalty has been reached, IPs are removed from the blocklist. IPs with a penalty of 16 are not removed. Suggest running this on a cron job to periodically cycle through the IP list.


1 = 1 minute

2 = 5 minutes

3 = 10 minutes

4 = 15 minutes

5 = 30 minutes

6 = 60 minutes (1 hour)

7 = 180 minutes (3 hours)

8 = 360 minutes (6 hours)

9 = 720 minutes (12 hours)

10 = 1440 minutes (1 day)

11 = 4320 minutes (3 days)

12 = 10080 minutes (7 days)

13 = 20160 minutes (14 days)

14 = 43200 minutes (30 days)

15 = 525600 minutes (1 year)

16 = indefinite

Run at command line

Block temporarily, penalty is incremented

./av2pa.py -a add -i

Block for 1 day

./av2pa.py -a add -i -p ’10’

Block indefinately

./av2pa.py -a add -i -p ‘~’


./av2pa.py -a remove -i


./av2pa.py -a exclude -i

Run Cron

* * * * * python path/to/your/av2pa.py

Script Settings


Set location of the blocklist (e.g ‘/var/www/block_inbound.txt’). This file should be https accessible if you intend to setup a Palo Alto External Dynamic List


Set a log file location (e.g ‘/var/log/block_inbound’)


Set the local timezone(e.g ‘America/Denver’)