Detect random sub-domain DNS query

Showing results for 
Show  only  | Search instead for 
Did you mean: 

Detect random sub-domain DNS query

L1 Bithead



I would like know if anyone has succesfull creating a custom signature either Custom spyware object or custom vulnerability signature to detect random sub-domain in DNS query.

For example:

We don't want to block or domain query.

But if there are query something like, we should detect and alert using Anti-spyware profile.


Can you recommend any solutions on how to solve this issue ?

This is particularly happened in ISP where they need to block this kind of sub-domain query which is not exist actually and consume DNS resources.






L5 Sessionator

Hi Yarianto,


I think from aspect of device OS and custom signatures you could probably craft something that would work for that purpose... you would match dns-req-section with regex pattern, but I am not sure where to start with this signature - you can ask them to give you regex of what they want to block and than test it as custom signature. I am not sure this would be my first approach for problem as you describe it, but I guess it could work, why not. What is their actual complaint, can't it be resolved on the DNS server itself?

Here is manual for custom signatures that explains dns-req-section. Note that at the end of the document you have reference to PAN-OS regex characters - it is a subset of what you would expect and there are no greedy expressions.


Best regards


  • 1 replies
Like what you see?

Show your appreciation!

Click Like if a post is helpful to you or if you just want to show your support.

Click Accept as Solution to acknowledge that the answer to your question has been provided.

The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!

These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the LIVEcommunity as a whole!

The LIVEcommunity thanks you for your participation!