How to exempt certain destinations from a File Blocking policy

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How to exempt certain destinations from a File Blocking policy

L2 Linker

I need to exempt certain sites from a policy that blocks downloads of executables, so downloads of executables are allowed from those sites. Since these are large sites that use content distribution networks, I can't create a policy with a destination IP address and a different security profile. What I would do with other brands of firewall that support FQDN object types, is reference the destination domain or URL in the policy instead of a destination IP, but Palo Alto doesn't have that feature yet. Is there a workaround I can use until Palo Alto supports the URL or FQDN object type?


Accepted Solutions

You will need to be at PAN-OS version 3.1.0 or higher to use the above custom AppID as it has enhancements to support the CN in SSL cert.

For PAN-OS version 3.0.x, please try the attached custom AppID.  The signature is looking for in the HTTP host header or the uri path.  You can almost separate the 2 matching conditions into 2 separate custom appIDs to suit your needs.

good luck.

Message was edited by: rmonvon

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L4 Transporter

The way to accomplish this with the current software would be to create a custom App-ID for the application/site and use that in the Application column of the policy with the appropriate file blocking profile. If you want help with the custom App-ID, post more info about the application/site and I am sure we can help you create it.

Given the dynamic nature of CDNs, FQDN objects are likely problematic for this. Most CDNs will use a very short TTL which will cause the entries to be out of sync as most firewalls expect this to be updated on a frequency typically in hours, not seconds.


So suppose I wanted to allow executable downloads from, but otherwise block them, how would I do that though App ID?

As far as the FQDN object types, I don't know how others such as Sonicwall do it, my guess is that it involves a lot of reverse DNS queries from the firewall. Is that feature still on track for later this year?



Attached is an example App-ID that includes two signatures. One that looks for in the host header of an HTTP request and one that looks for that applies to SSL traffic, looking at the CN in the servers SSL certificate. The values for could be replaced by whatever site you were want to have a unique App-ID for. Once created, this App-ID can be used in a policy and have the associated rule could have its own set of profiles attached.


When I import it, I get this error:

Config loaded from appid_microsoft_xml pattern-match unexpected here. Discarding. pattern-match unexpected here. Discarding.

It creates the new app, but it's missing the regular expression:

Should I enter something like "" under "Pattern" to apply to all microsoft URLs?


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