Suspicious DNS Query - how to find source computer?

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Suspicious DNS Query - how to find source computer?

Hi

Since I upgraded to 5.0.3 from 4.1.10 I started getting such entry in Treat log:

Suspicious DNS Query (Backdoor.rshot:app.pou.me) 4009473 spyware medium drop-all-packets 74

Suspicious DNS Query (Downloader.fik:encyklopedia.eduteka.pl) 4008620 spyware medium drop-all-packets 31

Suspicious DNS Query (generic:stor1173.uploaded.net) 4014899 spyware medium drop-all-packets 26

Bot: Torpig Phone Home DNS request 12657 spyware medium drop-all-packets 276

Suspicious DNS Query (generic:www.tns-counter.ru) 4000032 spyware medium drop-all-packets 40

It's pointing to my two DNS servers for my local networks. I'm almost sure that this isnt a problem with this servers because last week was Eastern Christmas and during this time I never got such traffic. When my users back to work its started again.

Some of user's computers are in the same Zone as this two DNS servers. How in this case catch sources of this traffic?

For other network I will enable strict Tread profile on allow DNS traffic rules, I hope that this will give me information about real sources of this dns requests.

With regards

Slawek

BCH
Not applicable

Re: Suspicious DNS Query - how to find source computer?

Have a look at the DNS servers' log files if available ? That should direct you to the client IPs requesting such hostnames.

L4 Transporter

Re: Suspicious DNS Query - how to find source computer?

Having your DNS server logs forwarded to a centralized location such as a log collector appliance or SIEM, or having full packet captures to an appliance (or both!) are two things that are essential in my mind for being able to effectively research events like these.

Here are two suggested ways of doing this "on the cheap" (the only cost is hardware and time essentially)

For the log collector/SIEM, an open source solution I can recommended is ELSA: enterprise-log-search-and-archive - Enterprise log search and archive (ELSA) is an industrial-stren...

"ELSA is a centralized syslog framework built on Syslog-NG, MySQL, and Sphinx full-text search. It provides a fully asynchronous web-based query interface that normalizes logs and makes searching billions of them for arbitrary strings as easy as searching the web. It also includes tools for assigning permissions for viewing the logs as well as email based alerts, scheduled queries, and graphing."

For an open source full packet capture solution, I've read about openfpc: openfpc - Open Full Packet Capture - Google Project Hosting

"OpenFPC is a set of scripts that combine to provide a lightweight full-packet network traffic recorder & buffering tool. It's design goal is to allow non-expert users to deploy a distributed network traffic recorder on COTS hardware while integrating into existing alert and log tools."

L4 Transporter

Re: Suspicious DNS Query - how to find source computer?

Hi

Thank you for your sugestion. For first step I will enable logs on my DNS serwers, if this doesnt help I will try to setup SIEM.

BCH
Not applicable

Re: Suspicious DNS Query - how to find source computer?

As for log collection or easier searches, you might want to try Splunk out (www.splunk.com), kinda easy to install and setup, with very straightforward searches (although the free version comes with a daily log limitation of 500MB :smileyhappy:).

L5 Sessionator

Re: Suspicious DNS Query - how to find source computer?

You can just enable the DNS signature PCAP for the spyware profile and view the PCAP clicking the PCAP icon in the threat logs.

P.S: Illustration performed on OS_5.0.x

DNS PCAP and EXception.PNG

DNS KB PCAP2.PNG

DNS PCAP-Capture.PNG

Regards,

Ameya

L4 Transporter

Re: Suspicious DNS Query - how to find source computer?

If the Palo Alto only saw the request from the DNS server out to the Internet and alerts on that traffic, wouldn't that still not provide enough info to track down the original client?

If you added a mirrored switch port of your LAN side network trwffic to a tap port on the PA, then the original client could be seen. Also if you segregated your DNS server from your clients into two separate VLANs and used the PA to route between them, you'd see the original traffic that way too.

Full packet capture / centralized logging is still the overall 'best practice' in my humble opinion :smileyhappy:

L4 Transporter

Re: Suspicious DNS Query - how to find source computer?

We are dealing with this issue now and we may not have access to DNS logs and we have a distributed DNS structure with an internal root DNS.  The root dns server may only be forwarding a request drom one of our distributed dns servers.  What we are looking is creating FQDN based objects for the DNS entries identified by PA and then putting those objects in a rule to block non DNS traffic.  This will identify the probable comprimised hosts.

Phil

L4 Transporter

Re: Suspicious DNS Query - how to find source computer?

>If the Palo Alto only saw the request from the DNS server out to the Internet and alerts on that traffic, wouldn't that still not provide enough info to track down the original client?

not, because klient and dns server are in the same security zone. That is my problem. Rest of my networks are separated, that one no.

I came up with idea: put on every policy from separated network security profile that will block such traffic. After that if I will have in logs warnings about thats mean that problem is from this one zone with DNS servers on it.

I also preparing for Splunk instalation. That could help me now and in the future.

Thank you for your help

L4 Transporter

Re: Suspicious DNS Query - how to find source computer?

I ran into similar situation with conficker spyware. The option is to enable logging on the DNS server to find out the original client. That is usually not possible due to high volume of logs. The other option is to SPAN/mirror your DNS server port and configure TAP on PAN. I have this configuration running in my network and it provides you with the real client ip address.

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