Backtrack 4: Information Gathering: DNS: Fierce – locate non-contiguous IP space and hostnames against specified domains
The final tool in the DNS Section is called fierce. It is a perl script written by rsnake. Fierce tries multiple techniques to find all the IP addresses and hostnames used by a target. These include – trying to dump the SOA records, do a zone transfer, searching for commonly used domain names with a dictionary attack, adjacency scan and a few more. Fierce is meant specifically to locate likely targets both inside and outside a corporate network. Only those targets are listed (unless the -nopattern switch is used). No exploitation is performed (unless you do something intentionally malicious with the -connect switch). Fierce is a reconnaissance tool. Fierce is a PERL script that quickly scans domains using several tactics.
Lets look at the help output to see what our options are:
root@666:/pentest/enumeration/fierce# ./fierce.pl -h fierce.pl (C) Copywrite 2006-2008 - By RSnake at http://ha.ckers.org/fierce/ Usage: perl fierce.pl [-dns example.com] [OPTIONS] Overview: Fierce is a semi-lightweight scanner that helps locate non-contiguous IP space and hostnames against specified domains. It's really meant as a pre-cursor to nmap, unicornscan, nessus, nikto, etc, since all of those require that you already know what IP space you are looking for. This does not perform exploitation and does not scan the whole internet indiscriminately. It is meant specifically to locate likely targets both inside and outside a corporate network. Because it uses DNS primarily you will often find mis-configured networks that leak internal address space. That's especially useful in targeted malware. Options: -connect Attempt to make http connections to any non RFC1918 (public) addresses. This will output the return headers but be warned, this could take a long time against a company with many targets, depending on network/machine lag. I wouldn't recommend doing this unless it's a small company or you have a lot of free time on your hands (could take hours-days). Inside the file specified the text "Host:n" will be replaced by the host specified. Usage: perl fierce.pl -dns example.com -connect headers.txt -delay The number of seconds to wait between lookups. -dns The domain you would like scanned. -dnsfile Use DNS servers provided by a file (one per line) for reverse lookups (brute force). -dnsserver Use a particular DNS server for reverse lookups (probably should be the DNS server of the target). Fierce uses your DNS server for the initial SOA query and then uses the target's DNS server for all additional queries by default. -file A file you would like to output to be logged to. -fulloutput When combined with -connect this will output everything the webserver sends back, not just the HTTP headers. -help This screen. -nopattern Don't use a search pattern when looking for nearby hosts. Instead dump everything. This is really noisy but is useful for finding other domains that spammers might be using. It will also give you lots of false positives, especially on large domains. -range Scan an internal IP range (must be combined with -dnsserver). Note, that this does not support a pattern and will simply output anything it finds. Usage: perl fierce.pl -range 111.222.333.0-255 -dnsserver ns1.example.co -search Search list. When fierce attempts to traverse up and down ipspace it may encounter other servers within other domains that may belong to the same company. If you supply a comma delimited list to fierce it will report anything found. This is especially useful if the corporate servers are named different from the public facing website. Usage: perl fierce.pl -dns examplecompany.com -search corpcompany,blahcompany Note that using search could also greatly expand the number of hosts found, as it will continue to traverse once it locates servers that you specified in your search list. The more the better. -stop Stop scan if Zone Transfer works. -suppress Suppress all TTY output (when combined with -file). -tcptimeout Specify a different timeout (default 10 seconds). You may want to increase this if the DNS server you are querying is slow or has a lot of network lag. -threads Specify how many threads to use while scanning (default is single threaded). -traverse Specify a number of IPs above and below whatever IP you have found to look for nearby IPs. Default is 5 above and below. Traverse will not move into other C blocks. -version Output the version number. -wide Scan the entire class C after finding any matching hostnames in that class C. This generates a lot more traffic but can uncover a lot more information. -wordlist Use a seperate wordlist (one word per line). Usage: perl fierce.pl -dns examplecompany.com -wordlist dictionary.txt
As you can see there are lots of options included in fierce.
lets try a regular query with the search flag:
(the search flag is useful if you are pretty sure of a subdomain name)
root@666:/pentest/enumeration/fierce# ./fierce.pl -dns remote-exploit.org --search mail DNS Servers for remote-exploit.org: ns2.icehosting.com ns1.icehosting.com Trying zone transfer first... Testing ns2.icehosting.com Whoah, it worked - misconfigured DNS server found: remote-exploit.org. 14400 IN SOA ns1.icehosting.com. root.remote-exploit.org. ( 2010030203 ; Serial 14400 ; Refresh 3600 ; Retry 1209600 ; Expire 86400 ) ; Minimum TTL remote-exploit.org. 14400 IN MX 10 mail2.remote-exploit.org. remote-exploit.org. 14400 IN MX 20 mail.remote-exploit.org. remote-exploit.org. 14400 IN A 184.108.40.206 remote-exploit.org. 14400 IN NS ns1.icehosting.com. remote-exploit.org. 14400 IN NS ns2.icehosting.com. balkan.remote-exploit.org. 14400 IN A 220.127.116.11 beta.remote-exploit.org. 14400 IN A 18.104.22.168 de.remote-exploit.org. 14400 IN A 22.214.171.124 es.remote-exploit.org. 14400 IN A 126.96.36.199 foo.remote-exploit.org. 14400 IN A 188.8.131.52 forum.remote-exploit.org. 14400 IN CNAME forums.remote-exploit.org. forums.remote-exploit.org. 14400 IN A 184.108.40.206 fr.remote-exploit.org. 14400 IN A 220.127.116.11 ftp.remote-exploit.org. 14400 IN A 18.104.22.168 it.remote-exploit.org. 14400 IN A 22.214.171.124 localhost.remote-exploit.org. 14400 IN A 127.0.0.1 mail.remote-exploit.org. 14400 IN A 126.96.36.199 mail2.remote-exploit.org. 14400 IN A 188.8.131.52 new.remote-exploit.org. 14400 IN A 184.108.40.206 oldwiki.remote-exploit.org. 14400 IN A 220.127.116.11 pop.remote-exploit.org. 14400 IN A 18.104.22.168 smtp.remote-exploit.org. 14400 IN A 22.214.171.124 www.remote-exploit.org. 14400 IN A 126.96.36.199 Okay, trying the good old fashioned way... brute force Checking for wildcard DNS... Nope. Good. Now performing 1896 test(s)... 188.8.131.52 beta.remote-exploit.org 184.108.40.206 de.remote-exploit.org 220.127.116.11 es.remote-exploit.org forum.remote-exploit.org alias forums.remote-exploit.org forums.remote-exploit.org address 18.104.22.168 22.214.171.124 forum.remote-exploit.org 126.96.36.199 forums.remote-exploit.org 188.8.131.52 fr.remote-exploit.org 184.108.40.206 ftp.remote-exploit.org 220.127.116.11 it.remote-exploit.org 127.0.0.1 localhost.remote-exploit.org 18.104.22.168 mail.remote-exploit.org 22.214.171.124 mail2.remote-exploit.org 126.96.36.199 new.remote-exploit.org 188.8.131.52 pop.remote-exploit.org 184.108.40.206 smtp.remote-exploit.org 220.127.116.11 www.remote-exploit.org Subnets found (may want to probe here using nmap or unicornscan): 127.0.0.0-255 : 1 hostnames found. 18.104.22.168-255 : 2 hostnames found. 22.214.171.124-255 : 6 hostnames found. 126.96.36.199-255 : 5 hostnames found. 188.8.131.52-255 : 1 hostnames found. Done with Fierce scan: http://ha.ckers.org/fierce/ Found 16 entries. Have a nice day.
This is a perfect example of a successful fierce session. We got a zone transfer and found a mis-configured nameserver. We also got a list of subdomains which we can compare against some of our other tools and we also got some subnets which we can do further checks on.
Fierce has many other options you can explore which can narrow down your results to only the relevant ones.