Password Cracking

This page focuses on turning a captured hash into a plaintext password. Every other page in this section, links back here rather than repeating command flags on every page.

Identify First

Cracking the wrong mode wastes time silently, hashcat and john just report no matches. Confirm the format before running anything.

Wordlist vs Mask

A wordlist (optionally mutated with rules) covers “probably a real word,” a mask attack covers “I know the structure” (company name + 4 digits, etc.). Pick based on what you actually know about the target.

Identifying the Hash

hashid -j <hash>        # candidate John the Ripper format(s)
hashid -m <hash>        # candidate hashcat mode number(s)

name-that-hash is a more actively maintained alternative, worth trying when hashid comes back empty or not correct:

nth --text '<hash>'

openwall’s sample hashes and pentestmonkey’s John hash-format cheat sheet are the fastest way to eyeball-confirm a format against a known example when the identifier tools disagree or guess wrong.

Weak/Unsalted Hashes: Try an Online Lookup First

MD5, SHA1, and NTLM are fast to compute and have no salt, which means the same plaintext always produces the same hash, so these specific hashes get precomputed and published in huge lookup databases. If the hash is one of these, checking it against a database takes seconds and is free, no GPU time spent, worth doing before reaching for cracking tool at all. A salted hash (bcrypt, sha512crypt, anything with a salt visible in the hash string) will never hit in these, every user’s hash is unique even for the same password, so skip straight to the next section for those.

Site	Covers
CrackStation	MD5, SHA1, SHA256, SHA512, NTLM, MySQL, and more; largest free precomputed table (~15 billion entries)
Hashes.com	Same idea, a different (and sometimes complementary) database, worth checking as a second source

Hashcat

Hashcat is GPU-accelerated and the right default choice whenever a GPU is available, orders of magnitude faster than John on anything but CPU-only boxes.

hashcat -m <mode> -a 0 <hash_file> <wordlist>     # -a 0: straight wordlist attack
hashcat -m <mode> -a 0 <hash_file> <wordlist> -r /usr/share/hashcat/rules/best64.rule   # with mutation rules
hashcat -m <mode> -a 3 <hash_file> '?u?l?l?l?l?d?d'   # -a 3: mask attack, see below

hashcat --show <hash_file>      # show already-cracked results from the potfile without re-running
hashcat -I                       # list available OpenCL/CUDA devices
hashcat -b                       # benchmark, useful for estimating how long a full crack will take

Common Hash Modes

Mode	Hash Type
0	MD5
100	SHA1
1400	SHA256
1700	SHA512
1000	NTLM
5600	NetNTLMv2
1800	sha512crypt (modern Linux `/etc/shadow`)
3200	bcrypt
13100	Kerberos 5 TGS-REP (Kerberoasting)
18200	Kerberos 5 AS-REP (AS-REP Roasting)
22000	WPA-PBKDF2 (WPA/WPA2 handshake)

Full mode list / example hashes for anything not covered above.

Mask Attack (`-a 3`)

Use when the password’s structure is known or guessable (a fixed prefix, a date suffix) rather than wasting time on a full wordlist.

Symbol	Charset
`?l`	lowercase a-z
`?u`	uppercase A-Z
`?d`	digits 0-9
`?h`	lowercase hex
`?H`	uppercase hex
`?a`	all of `?l?u?d?s` combined
`?b`	every byte, 0x00-0xff
`?s`	printable symbols

hashcat -a 3 -m 1000 hashes.txt '?u?l?l?l?l?l?d?d?d?d'   # e.g. "Summer2024"-shaped passwords

Generating a Mutated Wordlist Directly

Running a rule file against a base wordlist and saving the output (rather than feeding it live into hashcat) is useful when the same mutated list will be reused against multiple hash sets.

hashcat --force password.list -r /usr/share/hashcat/rules/best64.rule --stdout | sort -u > mutated.list

OneRuleToRuleThemAll is a far more thorough rule set than best64, worth switching to once a quick pass with best64 comes up empty.

John the Ripper

Still the right tool for anything hashcat doesn’t directly support, file-format hashes (SSH keys, Office documents, archives).

john --wordlist=<wordlist> <hash_file>
john --format=<format> --wordlist=<wordlist> <hash_file>   # force a format when auto-detection guesses wrong
john --incremental <hash_file>                               # brute force without a wordlist
john --single <hash_file>                                     # mutates account/field info already in the hash file itself
john <hash_file> --show                                        # show already-cracked results
john --list=formats                                              # list every supported format

locate *2john*          # list every extraction script John ships with

Extracting Hashes from Common File Types

Each of these follows the same pattern: extract a crackable hash from the file, run it through John, then show the result.

File Type	Extraction
SSH private key	`ssh2john.py id_rsa > ssh.hash`
PDF	`pdf2john.py file.pdf > pdf.hash`
Office (docx/xlsx)	`office2john.py file.docx > office.hash`
ZIP	`zip2john file.zip > zip.hash`
BitLocker	`bitlocker2john -i backup.vhd > backup.hashes` (then `grep "bitlocker\$0"` to isolate the right line)
Kerberos ticket (.kirbi)	`python2.7 kirbi2john.py ticket.kirbi`

john --wordlist=rockyou.txt ssh.hash
john ssh.hash --show

Cracking an Encrypted Archive by Brute Force

When no *2john extractor fits (a password-protected .gz/.tar.gz, for example), trying every password directly against the decompressor works just as well, just slower.

for pw in $(cat rockyou.txt); do openssl enc -aes-256-cbc -d -in archive.gz -k "$pw" 2>/dev/null | tar xz && echo "FOUND: $pw" && break; done

Quick Reference Tools

CrackStation

Free online hash lookup against a huge precomputed wordlist, worth trying before spending GPU time on a common hash.

name-that-hash

More actively maintained hash identifier than hashid.

OneRuleToRuleThemAll

The rule set to reach for once best64 comes up empty.

Hashcat Example Hashes

Full mode list with a real example of each hash type.

Get Started

Web

Linux

Windows

Active Directory

Services & Protocols

Password Attacks

Lateral Movement

Techniques

Tools & Resources

Password Cracking

Identify First

Wordlist vs Mask

Identifying the Hash

Weak/Unsalted Hashes: Try an Online Lookup First

Hashcat

Common Hash Modes

Mask Attack (`-a 3`)

Generating a Mutated Wordlist Directly

John the Ripper

Extracting Hashes from Common File Types

Cracking an Encrypted Archive by Brute Force

Quick Reference Tools

CrackStation

name-that-hash

OneRuleToRuleThemAll

Hashcat Example Hashes

Identify First

Wordlist vs Mask

​Identifying the Hash

​Weak/Unsalted Hashes: Try an Online Lookup First

​Hashcat

​Common Hash Modes

​Mask Attack (-a 3)

​Generating a Mutated Wordlist Directly

​John the Ripper

​Extracting Hashes from Common File Types

​Cracking an Encrypted Archive by Brute Force

​Quick Reference Tools

CrackStation

name-that-hash

OneRuleToRuleThemAll

Hashcat Example Hashes

Identifying the Hash

Weak/Unsalted Hashes: Try an Online Lookup First

Hashcat

Common Hash Modes

Mask Attack (`-a 3`)

Generating a Mutated Wordlist Directly

John the Ripper

Extracting Hashes from Common File Types

Cracking an Encrypted Archive by Brute Force

Quick Reference Tools