Blocking punycode URLs


Blocking punycode URLs

We have PA-820's and I have been looking for a way to leverage them to block punycode attacks.  In fact, we'd be pretty OK with blocking punycode URLs altogether.  I just haven't been able to puzzle out a way to do it.  If I add xn--* to the URL filter block list, it complains that I have multiple wildcards.  If it add just xn-- the firewall accepts it, but it just doesn't work, nothing is blocked.  It was the same result when I tried to create a custom URL category.  Is this something that can even be done at the firewall level, or should I look to address this on the DNS side?

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L7 Applicator

Re: Blocking punycode URLs


I am going to assume this is for outbound traffic. If yes then there are several things to do in conjunction.

In your Vulnerability profile, enable DNSSink hole.


Next I would block by web category, blocking the obvious bad stuff.

abused-drugs, adult, alcohol-tobacco, command and control, copyright-infingment, crypto-currency, dynamic-dns, hacking, high-risk, insufficient-content, malware, medium-risk, newly-registered-domin, not-resolved, parked, phishing, private-ip-address, proxy avoidance and anonymizers, questionable, shareware and freeware, unknown, web-advertisements


Externally have only your DNS servers be able to go our and get external DNS requests. Also use a secure service such as OpenDNS, cloudflare, Quad9, etc. And block the end users from exiting your environment over DNS externally.


Setup external dynamic lists, along with the PAN builtin ones, i have the following setup.

Source on PAN support:


Sans notes on this:


Others listed on this site:


Make sure you are performing SSL decrypt to ensure you are seeing the traffic.


This should get you started and not having to use a wildcard to block everything.



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