Understanding Password Hashes

Understanding Password Hashes

Why do operating systems store password hashes instead of plaintext passwords?

To verify login passwords without storing the plaintext password.

What happens when a user first sets a password?

The system computes and stores a hash of the password.

How does a system verify a submitted password?

Hash the supplied password and compare it with the stored hash.

What does a matching login hash indicate?

The password is accepted and the user is authenticated.

What does hash prime (hash′) mean in the password verification diagram?

The hash calculated from the password entered at login.

Which two Windows password hash types does the course cover?

LANMAN and NT.

Which Linux/UNIX password hashing options does the course list?

DES, MD5, SHA-256, SHA-512, and Yescrypt.

What is LANMAN (LM) hashing?

A weak legacy Windows password hashing mechanism.

Why can LANMAN appear on modern Windows networks?

Legacy compatibility retained during repeated upgrades.

What happens to letter case before LANMAN hashing?

All password letters are converted to uppercase.

To what total length does LANMAN pad a password?

14 bytes, using NULL bytes when needed.

How does LANMAN divide the padded password?

Into two separate 7-byte chunks.

Which encryption algorithm does LANMAN use for each chunk?

DES.

What fixed string do LANMAN DES operations encrypt?

KGS!@#$%

How is the final LANMAN hash formed?

Concatenate the two DES-encrypted 8-byte results.

Why is LANMAN easy to brute-force?

Uppercase conversion and independent 7-byte chunks reduce the search space.

Is LANMAN an acceptable modern password hashing algorithm?

No. The course considers it obsolete and insecure.

What is the modern Windows password hash type discussed in the course?

The NT hash.

Does NT hashing preserve uppercase and lowercase differences?

Yes. NT hashes are case-sensitive.

What preprocessing does NT hashing apply to a password?

Convert the password to Unicode if necessary.

Which hash function generates the NT hash?

MD4.

How long is an NT hash?

16 bytes (128 bits).

Where does Windows store local password hashes?

In the Security Accounts Manager (SAM).

What happens to LANMAN storage for passwords of 15 or more characters?

No LANMAN hash is stored; only the NT hash.

Do NT hashes use salts?

No.

How do NT hashes compare with LANMAN hashes?

Stronger than LANMAN, but still weak by modern standards.

Is NTLMv1 or NTLMv2 a password hashing algorithm?

No. NTLM is an authentication protocol; NT is the hash type.

Why might some tools call NT hashes NTLM hashes?

NT and NTLM are often used interchangeably in tool terminology.

What can identical unsalted password hashes reveal?

Two users chose the same password.

Why are unsalted hashes vulnerable to precomputed hash dictionaries?

The same password always produces the same stored hash.

What is a password salt?

A randomly chosen value combined with a password before hashing.

Is a password salt secret?

No. It is stored alongside the hash.

Does the user need to remember the salt?

No. The operating system handles it automatically.

Why do unique salts help protect users who share the same password?

Their identical passwords produce different hashes.

Why must a system store the salt?

To recompute the correct hash when verifying a login.

What security property does a randomly generated salt add?

Entropy, or randomness, to the hash input.

Which Active Directory database file contains domain credential data?

NTDS.dit.

Which registry hive is needed with NTDS.dit to extract hashes?

SYSTEM.

Why can an attacker not simply copy a live NTDS.dit with COPY?

It is in use exclusively by the OS and its contents are encrypted.

Which built-in Windows tool can back up Active Directory credential data?

ntdsutil.exe.

What ntdsutil command activates the AD DS database instance?

activate instance ntds

Which ntdsutil subcommand enters install-from-media mode?

ifm

Which ntdsutil command creates a full backup at C:\ntds?

create full c:\ntds (inside ifm mode).

What MITRE ATT&CK technique covers OS credential dumping?

T1003, OS Credential Dumping.

Which Impacket utility extracts hashes from an offline NTDS.dit backup?

secretsdump.py.

What does secretsdump.py -system specify?

The saved SYSTEM registry hive path.

What does secretsdump.py -ntds specify?

The saved NTDS.dit database file path.

What does LOCAL indicate at the end of the offline secretsdump command?

Use local saved database and hive files.

What is the offline Impacket command shown to extract domain hashes?

secretsdump.py -system registry/SYSTEM -ntds Active\Directory/ntds.dit LOCAL

Which Meterpreter command dumps local Windows password hashes?

hashdump

Can secretsdump.py extract local SAM hashes over SMB using admin credentials?

Yes, using Windows RPC services over SMB.

What remote secretsdump target format is shown in the course?

username:password@IP-address

Which Windows tool can extract hashes from logon process memory?

Mimikatz.

Which Mimikatz command requests debug privilege?

privilege::debug

Which Mimikatz command examines logon secrets and hashes?

sekurlsa::logonpasswords

Which PowerShell cmdlet filters Mimikatz output for Username or NTLM?

Select-String -Pattern 'Username|NTLM'

What command saves the Windows SAM hive to sam.hiv?

reg save hklm\sam sam.hiv

What command saves the Windows SYSTEM hive to system.hiv?

reg save hklm\system system.hiv

Which Mimikatz command parses offline SAM and SYSTEM hive files?

lsadump::sam /sam:sam.hiv /system:system.hiv

Why might an attacker analyze registry hives on a different Windows system?

To avoid running Mimikatz on the compromised endpoint.

What privilege is required for Windows hash-dumping techniques in this section?

Administrator access.

What security technology often detects or blocks hash-dumping tools?

Endpoint Detection and Response (EDR).

What is the order of fields in common Windows hashdump output?

username:userid:LANMAN:NTHASH

What hex string identifies an empty LANMAN hash?

aad3b435b51404eeaad3b435b51404ee

What hex string identifies an empty NT hash?

31d6cfe0d16ae931b73c59d7e0c089c0

What does a valid LM hash and a valid NT hash suggest?

A legacy LANMAN hash remains for the account.

What does an empty LM hash with a valid NT hash suggest?

LANMAN storage is disabled; the account still has an NT hash.

What can empty LM and empty NT hash fields indicate in the course example?

An inactive/disabled account or a failed hash extraction.

What mnemonic helps identify empty Windows password hashes?

Am All Day Baffled By Difficult Choices For Encrypted Data.

Where did early UNIX systems store password hashes?

/etc/passwd

Where do modern Linux systems store password hashes?

/etc/shadow

Which Linux account file remains world-readable?

/etc/passwd

Which user normally has permission to read /etc/shadow?

root

What hashing progression does the course describe for UNIX/Linux?

DES, MD5, SHA-256, SHA-512, then Yescrypt.

Which colon-separated field stores the hash in /etc/shadow?

The second field.

What character separates the hash type, salt, and hash in Linux crypt format?

The dollar sign ($).

Which Linux crypt prefix indicates MD5?

$$1$$

Which Linux crypt prefix indicates SHA-256?

$$5$$

Which Linux crypt prefix indicates SHA-512?

$$6$$

Which Linux crypt prefix indicates Yescrypt?

$$y$$

What prefix indicates legacy DES crypt in the course table?

No dollar-sign hash-type prefix.

What is the basic sequence of Linux crypt hash subfields?

Hash type, salt, then crypt-encoded password hash.

Is the character encoding of Linux crypt hashes exactly standard Base64?

No. It uses a modified Base64-like character set.

What are password hashing rounds?

Repeatedly applying the hash computation to increase work per guess.

How do multiple hash rounds affect legitimate logins?

They add a comparatively small delay.

How do multiple hash rounds affect offline password cracking?

They slow every password guess.

How many default rounds does Linux MD5 crypt use?

1,000.

How many default rounds does Linux SHA-256 crypt use?

5,000.

How many default rounds does Linux SHA-512 crypt use?

5,000.

How many MD4 rounds are used for the Windows NT hash?

One.

Why is NT hash cracking especially fast?

Single-round MD4 without a salt.

What hardware do attackers use to accelerate offline hash cracking?

Graphics Processing Units (GPUs).

Which tool does the course mention for GPU-based password cracking?

Hashcat.

Which password hashing algorithm is characterized as CPU-hard?

PBKDF2.

What does PBKDF2 stand for?

Password-Based Key Derivation Function 2.

What makes PBKDF2 computationally costly?

Configurable repeated HMAC calculations.

Which Wi-Fi security protocols use PBKDF2 for pre-shared key authentication?

WPA and WPA2.

How many SHA-1 rounds does the course specify for WPA/WPA2 PBKDF2?

4,096.

Which algorithms are both CPU-hard and memory-hard?

scrypt and Argon2.

Which algorithm won the 2015 Password Hashing Competition?

Argon2.