Hashcat

Hashcat is the de-facto GPU-accelerated password cracker — the offensive counterpart to John the Ripper, trading John’s broader format support and CPU flexibility for raw speed on modern AMD/NVIDIA hardware via OpenCL, HIP, or CUDA. It’s the standard tool for T1110.002 — Brute Force: Password Cracking, and accepts output from most dump tools directly (Metasploit hashdump, impacket secretsdump.py, Mimikatz .kirbi-derived TGS hashes).

Basic usage

hashcat -m $MODE -a $ATTACK $HASHFILE $WORDLIST

• -m $MODE — hash type (see table below; full list via hashcat --help or the example_hashes wiki).
• -a $ATTACK — attack mode: 0 straight wordlist, 1 combinator, 3 mask/brute, 6/7 hybrid wordlist+mask. Default is 0.
• -O — use an optimized kernel (faster, but limits candidate length — typically ≤32 chars for fast hashes, more for slow ones).
• -r rules/$RULE.rule — apply a mangling ruleset (e.g. best64.rule, d3ad0ne.rule, OneRuleToRuleThemAll.rule — the hashcat equivalent of John’s --rules).
• -w 3 (or 4) — workload profile; use -w 4 on a dedicated cracking rig, -w 2 if you’re sharing the GPU with a desktop.
• --show — print cracked hash:plaintext pairs from the potfile.
• --username — input lines contain user:hash (strip the username before cracking).

A raw hash can be passed directly in place of $HASHFILE (quote it; the shell loves to eat $ characters). Kali’s hash-identifier and hashid help identify an unknown blob; the hashcat example hashes page shows a canonical sample for every mode.

Common modes

Mode	Hash type
0	MD5
100	SHA1
900	MD4
1000	NTLM (Windows)
1400	SHA2-256
1700	SHA2-512
1710	SHA2-512 with salt (sha512($pass.$salt)) — format $HASH:$SALT
1800	UNIX sha512crypt $6$ (unix-password-hash-formats)
3000	LM (LANMAN)
3200	bcrypt $2*$
5500	NetNTLMv1
5600	NetNTLMv2
7500	Kerberos 5 AS-REQ Pre-Auth etype 23
13100	Kerberos 5 TGS-REP etype 23 (RC4) — kerberoasting
18200	Kerberos 5 AS-REP etype 23 — as-rep-roasting
19600	Kerberos 5 TGS-REP etype 17 (AES128)
19700	Kerberos 5 TGS-REP etype 18 (AES256)
19800	Kerberos 5 AS-REP etype 17
19900	Kerberos 5 AS-REP etype 18

A large set of “Raw Hash, Salted and/or Iterated” modes accept $HASH:$SALT — see the example_hashes wiki for the exact per-mode layout. Output is always HASH:PLAINTEXT tuples; the potfile (~/.hashcat/hashcat.potfile by default) records cracked pairs so re-running the same file is cheap — use --show rather than re-cracking.

A Token length exception almost always means the input line has the wrong shape: an extra field, a stray colon, a missing $ marker, or a hash that got truncated when copied out of a terminal (PowerShell’s console width truncation is the classic culprit for long TGS hashes — use Out-File -Width 8000).

Attack modes in practice

Wordlist (mode 0)

hashcat -m 1000 ntlm.txt /usr/share/wordlists/rockyou.txt -r rules/best64.rule

The workhorse. RockYou plus a mangling ruleset cracks the overwhelming majority of human-chosen passwords against fast hashes (NTLM, MD5).

Combinator (mode 1)

Concatenate every entry of wordlist A with every entry of wordlist B:

hashcat -m 1000 ntlm.txt -a 1 left.txt right.txt

The standalone combinator.bin from hashcat-utils pre-generates the combined list:

/usr/lib/hashcat-utils/combinator.bin $W1 $W2 > combined.txt

Mask / brute force (mode 3)

Masks describe a per-position character class:

Placeholder	Class
?l	lowercase
?u	uppercase
?d	digit
?s	special
?a	all printable ASCII
?b	0x00–0xff

# Generate all 4-digit PINs on stdout (no hash needed)
hashcat -a 3 ?d?d?d?d --stdout
 
# Crack an MD5 of a 4-digit PIN
hashcat -a 3 -m 0 $MD5_HASH ?d?d?d?d
 
# Crack NTLM where the policy is "8 chars, first uppercase, ends with two digits"
hashcat -a 3 -m 1000 ntlm.txt ?u?l?l?l?l?l?d?d

Custom classes go in --custom-charset1 (etc.) and are referenced as ?1.

Hybrid (modes 6 / 7)

Wordlist + mask (mode 6) or mask + wordlist (mode 7) — covers “password is a dictionary word plus a year/symbol suffix” better than pure rules:

hashcat -a 6 -m 1000 ntlm.txt rockyou.txt ?d?d?d?d

Consuming output from other tools

• Metasploit hashdump / post/windows/gather/smart_hashdump — feed the file with -m 1000 --username.

• Impacket secretsdump.py — same NTLM format, same -m 1000.

• Impacket GetUserSPNs.py -request — emits Hashcat-format -m 13100 lines directly; pipe to file and crack.

• Impacket GetNPUsers.py -request — emits -m 18200 AS-REP lines.

• Rubeus kerberoast — same -m 13100 format.

• /etc/shadow — -m 1800 (sha512crypt), -m 500 (md5crypt), etc. See unix-password-hash-formats for the $id$salt$hash anatomy.

• MySQL 8 mysql.user.authentication_string — the cached SHA2 (caching_sha2_password) value is a binary blob, not a crackable string. Convert it to hashcat mode 7401 (MySQL $A$ (sha256crypt)) in-database before extraction:

  SELECT CONCAT(
    '$mysql',
    LEFT(authentication_string, 6),
    '*',
    INSERT(HEX(SUBSTR(authentication_string, 8)), 41, 0, '*')
  ) FROM mysql.user WHERE user = 'target';

  Then crack with hashcat -m 7401 -O hash.txt rockyou.txt. The transformation re-wraps the raw bytes into the $mysql$TYPE*SALT*HASH layout hashcat expects; without it the blob is rejected with a token-length error.

• John’s .pot — John and Hashcat use incompatible potfile formats; extract cracked pairs via john --show and re-feed the uncracked hashes.

Comparing with John the Ripper

	Hashcat	John
Hardware	GPU-first (OpenCL/HIP/CUDA)	CPU-first (some GPU formats)
Format breadth	~300 modes	400+ formats (jumbo)
Speed on fast hashes (NTLM/MD5)	Typically 10–100× John on a decent GPU	Baseline
Speed on slow hashes (bcrypt/scrypt/yescrypt)	Comparable to John	Comparable to Hashcat
Wordlist rules	rules/*.rule files, similar syntax	Inline [List.Rules:…] in john.conf
Best at	High-volume fast-hash cracking (NTLM, NetNTLMv2, TGS-REP)	Long-tail formats (SSH keys, ZIP, RAR, keystore, …)

The natural workflow is to try Hashcat first (especially for kerberoasting, as-rep-roasting, NTLM from hashdump/mimikatz/impacket) and fall back to john-the-ripper for formats hashcat doesn’t support.

Sources

• hashcat — advanced password recovery
• hashcat/hashcat — GitHub Repository
• Hashcat example hashes
• Brute Force: Password Cracking, Sub-technique T1110.002 — MITRE ATT&CK

Related: john-the-ripper, kerberoasting, as-rep-roasting, unix-password-hash-formats, mimikatz, impacket, msfconsole, meterpreter, hydra, h8mail.