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.

Requirements:

The following CPAN modules are required:

• Net::DNS
• Net::hostent

perl -MCPAN -e 'install Net::DNS'

perl -MCPAN -e 'install Net::hostent'

It is available from here

Execution:

perl fierce.pl [-dns example.com] [OPTIONS]

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.com

-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

[root@localhost fierce]# perl fierce.pl -dns secure.com

DNS Servers for secure.com:

ns1.mydyndns.org

ns2.mydyndns.org

ns3.mydyndns.org

ns4.mydyndns.org

ns5.mydyndns.org

Trying zone transfer first...

Testing ns1.mydyndns.org

Request timed out or transfer not allowed.

Testing ns2.mydyndns.org

Request timed out or transfer not allowed.

Testing ns3.mydyndns.org

Request timed out or transfer not allowed.

Testing ns4.mydyndns.org

Request timed out or transfer not allowed.

Testing ns5.mydyndns.org

Request timed out or transfer not allowed.

Unsuccessful in zone transfer (it was worth a shot)

Okay, trying the good old fashioned way... brute force

Checking for wildcard DNS...

** Found 91772098723.secure.com at 195.238.237.142.

** High probability of wildcard DNS.

Now performing 1895 test(s)...