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John The Ripper | Cracking Password

John The Ripper | Cracking Password

Now as we have covered compilation and basics of John The Ripper its time for real password cracking. Now note that password cracking in John The Ripper depends on type of hash obtained. That means if you have obtained UNIX password hash then John The Ripper will crack it without problem, hash obtained from pwdump, then also John The Ripper will crack it without problem but if you have password hash encrypted like shadowing or hash obtained from authentication server
like Kerberos AFS you have to convert that files in John The Ripper format by using unshadow and unafs commands. Type commands as it is on command prompt and shell terminal to know how to use them.

The very first method to crack is default cracking method,

[root@localhost run~]#./john password.txt

It will crack password by using single crack mode and if it fails in single crack then it'll try word-list and lastly incremental mode.

The second method is using single crack mode. Now what is single crack mode, single mode crack is usually applied on passwords with similar patterns. For example,


Now look all passwords have similar pattern alphabets first, numerals after. Please note that this is just an example of patterns in password, there is no chance that pattern will be similar as I gave it in example. Usually no one keeps patterned password unless system administrator has explicitly mentioned it in password making rules. To crack password in single crack mode write any of these following command,

[root@localhost run~]#./john --single password.txt
[root@localhost run~]#./john -si password.txt

Now note that when you type complete word in UNIX system as an option you have to use “ -- ” and when abbreviation then ' - ' same also applies in John The Ripper so always use abbreviation since it saves your typing overhead.

Next type by which you can break password is using password dictionary. By default John The Ripperpassword.lst file in /john/run folder as default password list but when you use wordlist option, you have to manually specify password dictionary file, no matter the same file is kept as default password dictionary. uses

[root@localhost run~]#./john --wordlist=password.lst password.txt
[root@localhost run~]#./john -w=password.lst password.txt

You already know that dictionary of passwords work only on personal information of victim. But your victim might be a little cleaver and rather than using his password as it is he/she may have applied little character tweak. For example,


You can easily understand the password is jacob but written as j@c06, this kinda password is known as hybrid password and can be broken by applying mangling rules while attacking hash file with password list. This is how you can do it,

[root@localhost run~]#./john -w=password.lst -ru password.txt
[root@localhost run~]#./john -w=password.lst --rules password.txt

Now if you know the victim system uses only 8 characters for generating hashes then you can manually truncate password list to meet maximum 8 characters in each word in password list,

[root@localhost run~]#./john -w=password.lst -ru --stdout=8 | unique new_list.txt

Above command will create new_list.txt password list from password.lst by truncating all words in password.lst file to 8 characters.

Next password cracking method is known as incremental. This is brute force attack option and can be used as follows,

[root@localhost run~]#./john –incremental:alpha password.txt (brute force using only alphabets)

[root@localhost run~]#./john -i:digits password.txt (brute force using only numbers)

[root@localhost run~]#./john -i:all password.txt (brute force using all characters on keyboard)

There are other two options known as external and format. But as I am writing this for beginners I think I should give them leave on advanced options for now, so we will cover those options later in misc section. Till then if got any problem understanding above tutorial feel free to ask, thanks for reading and keep visiting.

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