DNS Sinkholing subdomains of known bad domains

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L1 Bithead

DNS Sinkholing subdomains of known bad domains

I tried to find an answer for this, but I couldn't find it. If someone has already posted this question, apologies...

 

I just turned DNS sinkholing and it works as expected for root domains, for example:

 

nslookup kntsv.nl returns the DNS sinkhole IP of 71.19.152.112.

 

BUT...

 

If I do an nslookup of any subdomain of kntsv.nl, it returns a valid A record, for example:

 

nslookup testing.kntsv.nl returns the IP of 109.72.85.37.

 

My question... Why did the dns lookup for the subdomain work but not the root? I would think the Palo would mark *.kntsv.nl as malicious and return with the sinkhole IP.

 

Thanks in advance for the help.

L7 Applicator

Re: DNS Sinkholing subdomains of known bad domains

When a root domain is malicious, it does not mean that automatically all subdomains are malicious.
As far as I know in the DNS signatures there are only FQDN's and not wildcard entries.
L2 Linker

Re: DNS Sinkholing subdomains of known bad domains

FYI, You should be able to create your own External Dynamic block list and add it to your DNS Sinkhole policy and wildcard the sub-domains if you want.
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