Sunday, October 15, 2017

Information Gathering: DNS Enumeration and Zone Transfer with Nslookup, Host, Dnsrecon, Dnsenum, Fierce , NSE and whois


- Layout for this exercise:

1 - Introduction

- DNS servers are some of the best sources for gathering information about a domain or an organization.

- DNS servers contain DNS and mail information for the domain with authority over what is provided when public requests are made from the Internet.

- Due to the abundant and interesting information contained in the DNS servers DNS Enumeration is one of the most critical steps while gathering information about a target.

- DNS Zone Transfer, also sometimes known by the inducing DNS query type AXFR, is a type of DNS transaction. 

DNS Zone Transfer is one of the many mechanisms available for administrators to replicate DNS databases across a set of DNS servers.

A zone transfer uses the Transmission Control Protocol (TCP) for transport, and takes the form of a client–server transaction. 

- The client requesting a zone transfer may be a slave server or secondary server, requesting data from a master server, sometimes called a primary server. 

- The portion of the database containing the list of all DNS names is the zone file.

- The data contained in a DNS zone may be sensitive from an operational security aspect. 

- This is because information such as server hostnames may become public knowledge, which can be used to discover information about an organization and even provide a larger attack surface.

2 - nslookup

- nslookup is a popular tool that queries name and email servers in the Internet given the domain:

- Applying the NS query option for name servers:

- Applying the MX query option for mail servers:

- Applying the ANY query option for both name and mail servers:

3 - host 

- host is a Linux command that performs powerful DNS lookups given a domain name:

- Without any other parameter host provides help:

- Looking for name servers (-t type ns):

- Looking for email servers (-t type mx):

- Looking for web servers :(-t type www):

4 - DNS Zone Transfer with host

- Now, let's use host for a little more complicated task like a DNS Zone Transfer.

- First, let's try with the previously enumerated ns1 name server. The zone transfer fails:

- However, the zone transfer with ns2 is successful:

- Finally the zone transfer with ns3 also fails:

- The result of the successful DNS Zone Transfer with ns2 is a full dump of the zone file for the whole domain, providing us a list of IPs and their corresponding DNS names.

- Let's try entering into a browser some of the IPs obtained from the DNS Zone Transfer:

5 - dnsrecon

- dnsrecon is an automated tool consisting of a Python script that can be user for DNS enumeration.

- Let's see that information provided by dnsrecon is the same as obtained before.

- First, dnsrecon detects the DNS servers ns1, ns2 and ns3:

- Then, dnsrecon tries a successful DNS zone transfer with ns2:

- Also, dnsrecon tries a DNS zone transfer with ns1 and ns3 with no result:

6 - dnsenum

- dnsenum is a multithreaded Perl script to enumerate DNS information of a domain.

- The output obtained with dnsenum is the same as before:

7 - fierce

- fierce is a Perl base script to perform DNS enumeration. Results obtained with fierce are pretty similar to previous ones:

8 - Nmap Scripting Engine (NSE)

 Nmap Scripting Engine (NSE) is an addition to Nmap which provides users with scripts to automate several tasks:

- The NSE dns-zone-transfer script provides same output than before:

- A little more limited result, because it finds just a list of common subdomains, is achieved with the NSE dns-brute.nse script:

9 - whois 

 - whois is a query and response protocol that is widely used for querying databases that store the registered users of an Internet resource, such as a domain name, an IP address block, or an autonomous system.

- Looking for the domain