I have been collecting different IP address for VoIP attacks in my infrastructure. These attacks happen every day multiple times. I have created a service which generates a notification to a python subscriber service which can then execute any action upon request.

Is it possible to add an ACL for each IP address that appears programmatically?. Example via a REST API to ASA. This is the JSON object I generate, I will just need to configure my python script to use the IP address and send a request to ASA to update ACL, in case IP address already there ignore.

{u'Content': u'', u'From': u'honeypot-ef4b6aa1-d5ca-43f8-92c8-f9840fb5bb9f-deadbeef'}
  • I think you'll have to do it from the CLI, with an Expect script (or similar).
    – Ron Trunk
    Feb 12, 2018 at 13:59

1 Answer 1


Although one way to do it is with programmatically updating an ACL, you might consider

This latter technique is written up here, and can be somewhat complex: https://www.cisco.com/c/dam/en/us/products/collateral/security/ios-network-foundation-protection-nfp/prod_white_paper0900aecd80313fac.pdf

It might be possible to do this with something much simpler such as RIP2 with next-hop filled in.

For the use you've indicated, it doesn't sound like you need it to be terribly fast, so I'd start with make-text-file-and-remotely-load it. The technique is extremely general and rather easy to do.

Run a script to create your ACL commands, probably periodically with cron or similar; then it issues

ssh edgerouter1 copy http://localserver/dynamicacl runing-config

Note that this "copy" is really a merge, in that it keeps the existing configuration except where the new config explicitely negates something with no access-list 22 or similar.

You need certificate-based login on the router for this to be practical.

[EDIT] While trying it I found a small surprise so added details. I tested with Cisco 2800 router with 15.1.4 as I have no ASA available, server was Ubuntu 16.

To repeat, this is a pretty general way of doing any programmatic configuration of Cisco devices. In general it's much better to have a fully non-interactive approach, rather than an expect-based approach. If the interactive system does something unusual your expect script can go wrong in very difficult-to-debug ways. If this programmed-copy goes wrong you issue the identical command by hand and debug from there.

Example network For example clarity, suppose your ASA/router inside address is and you have an internal web server available at

Generate config It's supposed you have a program badaddresses which produces a list of addresses you want to block. Make a formatter mkciscoacl in awk/python/whatever to produce your appropriate access list, which might look like this:

ip access-list extended autobad
 1 deny ip host any
 2 deny ip host any
 1000000 permit ip any any

Put on internal web Let's imagine you have a cron job which makes that file on the web server, available as

No-prompt Normally, when you do copy http://somewhere running-config you get a prompt confirming the target as running-config. This must be disabled in your configuration.

file prompt quiet

Certificate login You must have a certificate-based login available on your router, as you want the configuration to be entirely automatic. (Doc)

username autoloader priv 15 secret 12345 ! use a better one!
ip ssh pubkey-chain
  username autoloader
      ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDZahXX11Muz3ChJtmVvofZhv5T

Do whole thing Make a script dowholething.sh which does the whole thing

set -e
badaddresses | mkciscoacl > /var/www/html/cisco/automatic.conf
logger blahblah
ssh [email protected] \
  copy running-config

Automatic invocation On the web server, have a cron job like this:

* * * * * /path/to/dowholething.sh

Obviously you could do any configuration you like with this method. You might also consider source-based routing into a blackhole rather than straight blocking.

  • Thank you jonathanjo, by setting up 1 honeypot in AWS I have seen around 100 requests from different IP addresses and this is just 1 I plan to deploy ~20 in different datacenters and other cloud services... wondering if I can define in ASA a unique ACL which will grow eventually when I add these IP address programmatically ? (Example: using expect).
    – gogasca
    Feb 12, 2018 at 22:05

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