[Tutorial] nslookup,host,dig,whois: DNS Information Gathering – Penetration Testing

Information Gathering

Prior to an attack, the penetration tester should know as much as possible about the target environment and the characteristics of the system. The more targeted information the penetration tester finds, the better the chances of identifying the easiest and fastest way to succeed. Black-box testing requires more reconnaissance than white-box testing because testers do not get too much data. Scouting services may include Internet footprints for investigating targets, monitoring resources, monitoring personnel, processes, etc., scanning network information (such as IP addresses and system types), and social engineering public services such as help desks. Reconnaissance is the first step in penetration testing, whether the penetration tester is known to confirm the target system, or to find known intelligence. When reconnaissance, the target environment must be defined according to the work area. Once the target is identified, a survey is performed to gather information about the target, such as which ports are used for communication, where the target is hosted, what services it provides to the customer, and so on. This data can be used to develop a plan to see what the best way to get the desired results. The results of the reconnaissance process should include a list of all target assets, what applications are associated with the asset, services to be used, and possible asset owners. Kali Linux provides a category labeled “Information Gathering”, which is a reconnaissance resource. Tools include tools for investigating networks, data centers, wireless networks, and host systems. The following is a checklist of reconnaissance goals: Acknowledging the goals Defining the use of applications and services Acknowledging the type of system, confirming the available ports, confirming the running services, social engineering informat7ion, document discovery.

On this posting, I’m going to guide how to gather DNS information using nslookup, host, dig & whois


Nslookup is a command line tool included with most operating systems that allows a user to look up a network name server, as well as return IP addresses and domain names for a network server.


Non-interactive mode
Query IP of domainQuery domain name DNS service provider
Query mail server

Interactive mode


host is a simple utility for performing DNS lookups. It is normally used to convert names to IP addresses and vice versa. When no arguments or options are given, host prints a short summary of its command line arguments and options.


host: illegal option — h
Usage: host [-aCdlriTwv] [-c class] [-N ndots] [-t type] [-W time]
[-R number] [-m flag] hostname [server]
-a is equivalent to -v -t ANY
-c specifies query class for non-IN data
-C compares SOA records on authoritative nameservers
-d is equivalent to -v
-l lists all hosts in a domain, using AXFR
-i IP6.INT reverse lookups
-N changes the number of dots allowed before root lookup is done
-r disables recursive processing
-R specifies number of retries for UDP packets
-s a SERVFAIL response should stop query
-t specifies the query type
-T enables TCP/IP mode
-v enables verbose output
-w specifies to wait forever for a reply
-W specifies how long to wait for a reply
-4 use IPv4 query transport only
-6 use IPv6 query transport only
-m set memory debugging flag (trace|record|usage)
-V print version number and exit


dig (which stands for domain information groper) is a flexible tool for interrogating DNS name servers. It performs DNS lookups and displays the answers that are returned from the name server(s) that were queried. Most DNS administrators use dig to troubleshoot DNS problems because of its flexibility, ease of use and clarity of output. Other lookup tools tend to have less functionality than dig.


Usage: dig [@global-server] [domain] [q-type] [q-class] {q-opt}
{global-d-opt} host [@local-server] {local-d-opt}
[ host [@local-server] {local-d-opt} […]]
Where: domain is in the Domain Name System
q-class is one of (in,hs,ch,…) [default: in]
q-type is one of (a,any,mx,ns,soa,hinfo,axfr,txt,…) [default:a]
(Use ixfr=version for type ixfr)
q-opt is one of:
-4 (use IPv4 query transport only)
-6 (use IPv6 query transport only)
-b address[#port] (bind to source address/port)
-c class (specify query class)
-f filename (batch mode)
-i (use IP6.INT for IPv6 reverse lookups)
-k keyfile (specify tsig key file)
-m (enable memory usage debugging)
-p port (specify port number)
-q name (specify query name)
-t type (specify query type)
-u (display times in usec instead of msec)
-x dot-notation (shortcut for reverse lookups)
-y [hmac:]name:key (specify named base64 tsig key)
d-opt is of the form +keyword[=value], where keyword is:
+[no]aaonly (Set AA flag in query (+[no]aaflag))
+[no]additional (Control display of additional section)
+[no]adflag (Set AD flag in query (default on))
+[no]all (Set or clear all display flags)
+[no]answer (Control display of answer section)
+[no]authority (Control display of authority section)
+[no]besteffort (Try to parse even illegal messages)
+bufsize=### (Set EDNS0 Max UDP packet size)
+[no]cdflag (Set checking disabled flag in query)
+[no]cl (Control display of class in records)
+[no]cmd (Control display of command line)
+[no]comments (Control display of comment lines)
+[no]crypto (Control display of cryptographic fields in records)
+[no]defname (Use search list (+[no]search))
+[no]dnssec (Request DNSSEC records)
+domain=### (Set default domainname)
+[no]edns[=###] (Set EDNS version) [0]
+ednsflags=### (Set EDNS flag bits)
+[no]ednsnegotiation (Set EDNS version negotiation)
+ednsopt=###[:value] (Send specified EDNS option)
+noednsopt (Clear list of +ednsopt options)
+[no]expire (Request time to expire)
+[no]fail (Don’t try next server on SERVFAIL)
+[no]identify (ID responders in short answers)
+[no]ignore (Don’t revert to TCP for TC responses.)
+[no]keepopen (Keep the TCP socket open between queries)
+[no]multiline (Print records in an expanded format)
+ndots=### (Set search NDOTS value)
+[no]nsid (Request Name Server ID)
+[no]nssearch (Search all authoritative nameservers)
+[no]onesoa (AXFR prints only one soa record)
+[no]opcode=[###] (Set the opcode of the request)
+[no]qr (Print question before sending)
+[no]question (Control display of question section)
+[no]recurse (Recursive mode)
+retry=### (Set number of UDP retries) [2]
+[no]rrcomments (Control display of per-record comments)
+[no]search (Set whether to use searchlist)
+[no]short (Display nothing except short
form of answer)
+[no]showsearch (Search with intermediate results)
+[no]split=## (Split hex/base64 fields into chunks)
+[no]stats (Control display of statistics)
+subnet=addr (Set edns-client-subnet option)
+[no]tcp (TCP mode (+[no]vc))
+time=### (Set query timeout) [5]
+[no]trace (Trace delegation down from root [+dnssec])
+tries=### (Set number of UDP attempts) [3]
+[no]ttlid (Control display of ttls in records)
+[no]vc (TCP mode (+[no]tcp))
global d-opts and servers (before host name) affect all queries.
local d-opts and servers (after host name) affect only that lookup.
-h (print help and exit)
-v (print version and exit)


WHOIS is an Internet utility that shows the user additional information about a domain, the registrar of the domain, and the IP address.


whois: option requires an argument — ‘h’
Usage: whois [OPTION]… OBJECT…

-h HOST, –host HOST connect to server HOST
-p PORT, –port PORT connect to PORT
-H hide legal disclaimers
–verbose explain what is being done
–help display this help and exit
–version output version information and exit

These flags are supported by whois.ripe.net and some RIPE-like servers:
-l find the one level less specific match
-L find all levels less specific matches
-m find all one level more specific matches
-M find all levels of more specific matches
-c find the smallest match containing a mnt-irt attribute
-x exact match
-b return brief IP address ranges with abuse contact
-B turn off object filtering (show email addresses)
-G turn off grouping of associated objects
-d return DNS reverse delegation objects too
-i ATTR[,ATTR]… do an inverse look-up for specified ATTRibutes
-T TYPE[,TYPE]… only look for objects of TYPE
-K only primary keys are returned
-r turn off recursive look-ups for contact information
-R force to show local copy of the domain object even
if it contains referral
-a also search all the mirrored databases
-s SOURCE[,SOURCE]… search the database mirrored from SOURCE
-g SOURCE:FIRST-LAST find updates from SOURCE from serial FIRST to LAST
-t TYPE request template for object of TYPE
-v TYPE request verbose template for object of TYPE
-q [version|sources|types] query specified server info

The post [Tutorial] nslookup,host,dig,whois: DNS Information Gathering appeared first on Penetration Testing.

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