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| # |__| |____|_||______||______||_| \_/ |_______/|____/ |__|\__||_____| |
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| A tool to collect DNS records passively to aid Incident handling, Network |
| Security Monitoring (NSM) and general digital forensics. |
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| 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. |
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| Example output from version 1.0.0->Current in the log file (/var/log/passivedns.log): |
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| #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 |
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| PassiveDNS works on IPv4 and IPv6 traffic and parse DNS traffic over TCP and UDP. |
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| ** How can PassiveDNS be used: ** |
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| Typical usages: |
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| 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... |
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| But using PassiveDNS data, quering the domain, you get following history: |
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| 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 |
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| 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... |
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| 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. |
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| 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. |
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| 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 :) |
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| Questions, suggestions, sugar or flame is always welcome :) |
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| I hope PassiveDNS gives you a new tool to fight malware and its herders... |
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| (c)2011-2020 - Edward Bjarte Fjellskål |
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