# Blister
# Author: Andrew T. Withers (atw31337@gmail.com)
# Description: This script will download and parse blacklists into ASA configuration format and output the commands as a text file. 
# The text can then be pasted into an ASA CLI terminal. Blacklist compatiblity format is as follows.
# Commented lines, lines starting with a '#', will be ignored. All other lines must either contain a valid IPv4 or IPv6 address
# (192.168.1.0, fd08:23eb:5a25:7df1:0000:0000:0000:0001), an IPv4 subnet in CIDR notation (192.168.1.0/24), or an IPv4 range
# (192.168.1.0-192.168.1.55). An FQDN function has been added to enable the parsing of URL blacklists. Any URLs containing
# wildcards will be removed because the ASA does not allow them to be used in FQDNs. Lists that follow these formats can be
# added or removed in the blacklists file. The DShield block list does not follow this format; however, I have added a case specific
# function for this particular list.
##########################################################################################################################################

Instructions and notes:

Create an object group for blacklisted IP addresses on the ASA firewall. Add it to your ACL as an explicit deny rule. This will be the object
group that you will enter into the configuration when prompted. Every time the script is run, it first searches for a configuration file. 
If it does not find a configuration it will prompt the user for the necessary information and create a configuration file for future use. 
Blacklists can be added or removed from /opt/blister/blacklists once the initial configuration is complete. The script will create an object 
group for each individual list and add that group to the blacklisted IPs object group specified in the config. When adding lists to the blacklists file
they should be entered in the following format: ObjectGroupName=URL. The ObjectGroupName can be anything you want it to be but should probably describe the
blacklist which it contains. The blacklists file contains a number of default lists which can be used for reference. Use the -h option to display 
the available options. If you opt to receive the output via email I suggest using the -a option to have it sent as an attachment.
The output can be quite lengthy which can cause issues for web-based email. Using the attachment option also prevents the email client from converting 
URLs into "safelinks." Once you have received and copied the output from the script, log into an ASA terminal, enter enable mode and paste. 
Configuration changes can be made by modifying /etc/blister.conf. Blister is multi-threaded (multi-process); however, each thread only works 
on one list at a time. Only one instance of blister can run at a time. The script will notify you if another instance is already running. This is done
to ensure that multiple instances are not writing to the same output file at the same time.

Please feel free to contact me with any questions, issues, or suggestions at the email address above.