The Lazy Networker

A pass-the-hash attack is a cybersecurity attack in which a malicious user steals hashed credentials from a compromised system and uses them to log in as the original user.

Hashing is an essential concept in cybersecurity and computer science. It involves using a mathematical algorithm, a hash function, to convert input data into a hash value. This process is deterministic and one-way, meaning it cannot be reversed to reveal the original data. i.e, It is not possible to get a clear-text password from a password hash.

On local systems, Windows stores passwords in a hashed, encrypted format in the Security Accounts Manager (SAM) database and caches them in LSASS(Local Security Authority Subsystem Service) memory during logon. If a malicious user obtains a password hash, they can execute a pass-the-hash attack.

NTLM (NT LAN Manager) is a Windows authentication protocol that uses a challenge-response mechanism. Instead of sending a password over the network, the client proves it knows the password by encrypting a server-issued challenge with the password’s hash (as a DES key)

The server verifies this response using its stored hash.

In a Pass-the-hash attack, the attacker exploits a vulnerability in the NTLM protocol to gain unauthorised access. The attacker does not need to know the clear-text password, as NTLM will accept the hash as proof of identity. He will pass the hash he obtained and will be allowed access as a legitimate user.

. Attackers can steal these hashes through various methods

1. Memory dumping: They can extract hashes from the LSASS process’s memory using Mimikatz and Procdump.\
2. Stealing SAM database: If an attacker has access to SAM, they could dump the hash from it.
3. Malware – key loggers, rootkits can give them access to hashes.
4. Active directory compromise.
5. Packet sniffing.

NTLM is mainly kept for backward compatibility in Windows. Current versions of Windows primarily use Kerberos for domain authentication, but NTLM is still used where a system is not part of a domain.

Because of its vulnerability, Microsoft recommends disabling NTLM wherever possible.

Implementing a zero-trust architecture is the most effective way to prevent pass-the-hash attacks. Stick to the following to secure your Pc/network.

1. Strong authentication and identity verification – implement MFA.
2. Least privilege and Just-in-Time Access control.
3. Continuous monitoring and anomaly detection