I’ve been playing around with the Citrix ADC IP Reputation feature – https://docs.citrix.com/en-us/citrix-adc/13/reputation/ip-reputation.html in the lab for some time and to be honest it’s such a small but very effective feature which I almost never see active, why is that?
If you’ve gotten a premium licensed ADC appliance it’s a simple right click>enable and you put in the necessary arguments in a responder policy. See the following article for a quick how to video – https://www.youtube.com/watch?v=WedxwiEVuG4 and basically that is it. The requests are going to be filtered on a Webroot service provider for malicious IP database and you can then drop those from ever getting at you network. (and put in a nifty log action so that you can filter as a syslog entry in Citrix ADM
I put a global responder in place with the expression: CLIENT.IP.SRC.IPREP_IS_MALICIOUS and a reset with accompanied log entry: CLIENT.IP.SRC + ” connection was dropped by Responder Action for malicious IP when accessing ” + HTTP.REQ.URL the results were pretty much mind blowing, see the following screenshot:Since the exploit CVE-2019-19781 – Vulnerability in Citrix Application Delivery Controller, Citrix Gateway, and Citrix SD-WAN WANOP appliance – https://support.citrix.com/article/CTX267027 the focus was pretty much around that but with the above rule in place I got more hits on the reputation feature than on the mitigation responder in that time. (And these are probes/attacks we don’t know about!)
So to sum it up this is a very good starting point if something like Application Firewall is a bridge to far but most definitely will improve your security with a simple setup.
Hope it helps.