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https://github.com/gamelinux/passivedns

A network sniffer that logs all DNS server replies for use in a passive DNS setup
https://github.com/gamelinux/passivedns

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A network sniffer that logs all DNS server replies for use in a passive DNS setup

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A tool to collect DNS records passively to aid Incident handling, Network

Security Monitoring (NSM) and general digital forensics.



PassiveDNS sniffs traffic from an interface or reads a pcap-file and outputs

the DNS-server answers to a log file. PassiveDNS can cache/aggregate duplicate

DNS answers in-memory, limiting the amount of data in the logfile without

losing the essense in the DNS answer.



Example output from version 1.0.0->Current in the log file (/var/log/passivedns.log):



#timestamp||dns-client ||dns-server||RR class||Query||Query Type||Answer||TTL||Count

1322849924.408856||10.1.1.1||8.8.8.8||IN||upload.youtube.com.||A||74.125.43.117||46587||5

1322849924.408857||10.1.1.1||8.8.8.8||IN||upload.youtube.com.||A||74.125.43.116||420509||5

1322849924.408858||10.1.1.1||8.8.8.8||IN||www.adobe.com.||CNAME||www.wip4.adobe.com.||43200||8

1322849924.408859||10.1.1.1||8.8.8.8||IN||www.adobe.com.||A||193.104.215.61||43200||8

1322849924.408860||10.1.1.1||8.8.8.8||IN||i1.ytimg.com.||CNAME||ytimg.l.google.com.||43200||3

1322849924.408861||10.1.1.1||8.8.8.8||IN||clients1.google.com.||A||173.194.32.3||43200||2



PassiveDNS works on IPv4 and IPv6 traffic and parse DNS traffic over TCP and UDP.



** How can PassiveDNS be used: **



Typical usages:



1) Search for domain or IP history when working on an incident.

   Example:

   Company has malware talking to bad.twittertoday.com.

   At current time, the domain is resolving to say 202.29.94.200

   You search your Flowdata and find the clients talking to that IP and

   remidate. You look at the Flowdata, and you discover that the date

   and time the clients first talked to that IP, and concludes that as

   the time of infection...



   But using PassiveDNS data, quering the domain, you get following history:



 FirstSeen  | LastSeen   | TYPE | TTL |        Query         |   Answer

----------------------------------------------------------------------------

 2011-12-01 | 2011-12-11 |    A |  60 | bad.twittertoday.com |  71.51.115.11

 2011-12-11 | 2011-12-18 |    A |  60 | bad.twittertoday.com |     127.0.0.1

 2011-12-18 | 2012-01-14 |    A |  60 | bad.twittertoday.com | 202.29.94.200



   Going back and searching for 71.51.115.11 in your Flowdata, you find

   traffic back to the FirstSeen data, and you also see more clients

   initially infected (so you did not manage to remidate/check out all your

   clients in the first run by just looking at IP 202.29.94.200). Doing

   forensics on the the clients you missed in the first run, reveals that

   they have downloaded a different malware and deleted the initial one,

   that beeing the reason you did not see flows from them to 202.29.94.200.

   The new malware gives you new domains and IPs to go look for...



2) Say you have an indication of malicious C&C traffic going to an IP on

   port 80. The domain used by the alleged malware is supposed to be

   cc.twittertoday.com. Searching you Flowdata, reveals lots of clients

   talking to that IP, and you might think that the whole company is p0wned.

   A quick search in your PassiveDNS DB shows you that the IP in question is

   also hosting 300 + websites and you might even spot a website hosted on

   that IP that you are familiar with and that you know lots of people in the

   company would legit visit daily.

   Searching your PassiveDNS DB gives you no hits for the domain in question,

   hopefully meaning that you dont have that malware talking to that domain

   in your network.



3) You know that *.twittertoday.com are often used in malware and the

   subdomains change randomly. Many have rules for such domains in their

   IDS/IPS, sucking up unnecessary juice from the systems. Having a script

   pre-loaded with a list of regexp of domains and subdomains to watch for

   and giving you an alert when they hit will give you much better detection

   on threat based on domains.



   You can also do a whois for all new top domains seen, correlate the whois

   info with a list of know bad info, such as the name of the person or

   company that has registered the domain, telephone/fax numbers, address

   and so on, ending up with a score that might be high enough for triggering

   an alert to you :)



Questions, suggestions, sugar or flame is always welcome :)



I hope PassiveDNS gives you a new tool to fight malware and its herders...



(c)2011-2020  -  Edward Bjarte Fjellskål