When it comes to choosing a password, it always comes at the worst possible time.
And since, moreover, it is necessary to remember it... passwords are often based on simple notions: first name, brand, memory...

Fortunately, security managers impose password management policies designed to prevent these abuses...
Well, ...
In 90% of the cases, the capital letter is at the beginning of the password, the numbers and the special character at the end...
Please stop using Ferrari12$ as password...

RockYou, a California based company, made it possible to authenticate on facebook applications without having to re-enter passwords. In December 2009, it was hacked.

The database containing the unencrypted names and passwords of its 32 million customers was stolen and then made public.
An analysis of the passwords showed that two thirds of the passwords were less than 6 characters long, and that the most commonly used password was 123456.

This list of passwords, sorted by frequency is frequently used in CTF.
On Kali, the file, zipped, is stored in: /usr/share/wordlists/
In the terminal, to get into good habits, the file can be found at: /usr/share/wordlists/rockyou.txt

password list Rockyou: rockyou.txt

To find out if your email address is present in a data leak, use the Firefox Monitor service.

A professional never keeps a password.
It records a hash.

A hash is generated by a mathematical function from the user's password.
When the user enters his password, the software calculates the hash and sends it to the server which compares it with the hash it has stored. If the two hashes match, then the user knows the password, and is authenticated. If someone sniffs the messages, he won't see the password, just the Hash.
Knowing the Hash, it is complicated to retrieve the password.
To calculate a Hash of the password '123456' with the MD5 function, use the following command in the terminal :
$ printf '123456' | md5sum
123456 will always give the same MD5 Hash.

The MD5 function has been widely used in the past, but the power of today's processors requires the use of more complex functions to be cracked such as SHA1, SHA256 or SHA512.
. The size of the hash increases with the complexity of the algorithm.

printf '123456' | sha1sum

printf '123456' | sha256sum

Note: we use 'printf' and not 'echo' for a hash calculation. Echo adds a line break which is taken into account by the Hash.

Longer Hashes are more complicated to break, but it is still possible to pre-calculate them for common passwords such as the ones found in RockYou list.

To avoid the pre-calculation of Hash, we use Salts.
These are additional values that are added at the beginning of the password before calculating the Hash.
The hash check remains fast, but the pre-calculated tables become useless, they have to be recalculated for each Salt.

Compute the hash of 123456, with the Salt ABCDE, and the Hash MD5 function in python:

$ python3 -c "import crypt; print(crypt.crypt('123456', '$1$ABCDE$'))"

With openssl: -1: MD5 password, -5:SHA256 and -6:SHA512

$ openssl passwd -1 -salt ABCDE  123456

The result is : $1$ABCDE$Kn5RIMYO1QXy7GtJysNSC1
Composed by three fields $xx$xx$xx :
$1 : hash function is MD5 ($5 SHA256, $6 SHA512)
$ABCDE : Salt
$Kn5RIMYO1QXy7GtJysNSC1 : MD5 hash of 123456+salt

Use online services to crack hash:

Try: e10adc3949ba59abbe56e057f20f883e

The /etc/passwd file is a text file with each line describing a user account.
Each line consists of seven fields separated by a colon.
Here is an example of a recording:

jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8910,(234)5550044,email:/home/jsmith:/bin/sh
  • jsmith: login name.
  • x : a x means password hash is stored in the /etc/shadow file, which is only readable by the root account. A * prevents connections from an account while keeping its username. In early versions of unix, this field contained the cryptographic hash of the user's password.
  • 1001 : UID - User ID
  • 1000 : GID - Group ID. A number, identifying the user main group.
  • Joe Smith,Room 1007,(234)555-8910,(234)5550044,email : Gecos field. A comment that describes the person or account. Usually a comma-separated set of values, providing the user's full name and contact information.
  • /home/jsmith : account home directory.
  • /bin/sh : shell program used by the user. Can be nologin.

The first lines of the file are usually system accounts.
User accounts are often described in the last lines.
This file allows to quickly identify users, applications (tomcat, mysql, www_data,...), their working directories, and whether or not they have access to a shell.


John The ripper allows to check if a hash corresponds to a password present in a list.

Save one or more hashes in hash.txt file.

$ echo 'root:$1$1337$WmteYFHyEYyx2MDVXln7Y1' >hash.txt
$ echo 'wordpressuser1:$P$BqV.SQ6OtKhVV7k7h1wqESkMh41buR0' >>hash.txt

Use John the ripper to break the password using its internal password list:

$ john hash.txt

Use John the ripper to break the password using the Rockyou list:

$ john hash.txt --wordlist=/etc/share/wordlists/rockyou.txt

John no longer displays passwords he has already broken.
To view these passwords:

$ john hash.txt --show 

There are several versions of John on the Internet. The Kali and Parrot distributions, install the John Community Enhanced -jumbo version. This distribution is available at

$ sudo snap install john-the-ripper
$ john
John the Ripper 1.9.0-jumbo-1 OMP [linux-gnu 64-bit 64 AVX2 AC]

Bruteforce /etc/shadows with John:

$ unshadow /etc/passwd /etc/shadow > hash.txt  
$ john hash.txt --wordlist=/etc/share/wordlists/rockyou.txt 
$ john hash.txt --show 

Bruteforce MySQL Hash with John:

mysql -u dbuser -p drupaldb 
 show databases; 
 show tables; 
 select name, pass from users; 
 | name  | pass                                                    | 
 |       |                                                         | 
 | admin | $S$DvQI6Y6xxxxxxxxxxxxxxxxxxxxxxxxxEDTCP9nS5.i38jnEKuDR | 
 | Fxxxx | $S$DWGrxefxxxxxxxxxxxxxxxxxxxxxxxxxxxx3QBwC0EkvBQ/9TCGg | 
 | ..... | $S$Drpxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/x/4ukZ.RXi | 

echo '$S$DWGrxefxxxxxxxxxxxxxxxxxxxxxxxxxxxx3QBwC0EkvBQ/9TCGg'>hash.txt 
$ john hash.txt --wordlist=/etc/share/wordlists/rockyou.txt 
$ john hash.txt --show 

Bruteforce a pasword protected id_rsa id (id used for ssh connections):

RSA header:

Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,2AF25325A9B318F344B8391AFD767D6D


Let check if the password is in the Rockyou list.
$ python /usr/share/john/ id_rsa > id_rsa.hash $ john --wordlist=/usr/share/wordlists/rockyou.txt id_rsa.hash $ john hash.txt --show

Many software and equipment are installed with default configurations and passwords.
Very often, these passwords are not changed..

Vendor          Username      Password
------          --------      --------
Raspberrypi     pi            raspberry
3COM            BLANK         12345
APACHE          admin         jboss4
Apache          admin         tomcat
Apache          tomcat        tomcat
Adobe           admin         admin
Airlink         BLANK         admin
Apple           admin         public
Belkin          admin         none
Borland         politically   correct
Bunker OS       BLANK         123456
Cisco           EAdmin        BLANK
Cisco           BLANK         Cisco
D-Link          BLANK         private
Del             Administrator storageserver
Edimax          admin         123
F5              admin         admin
kali            kali          kali 
Netgear         BLANK         password
parrot          user          toor 
Raspberrypi     pi            raspberry
ubuntu          user          BLANK