What happened
NTLMv1 authentication weaknesses were exploited using rainbow tables to recover password hashes from captured challenge-response data. Attackers leveraged precomputed rainbow tables to crack NTLMv1 hashes, significantly reducing the time required to recover plaintext passwords. The technique relies on intercepting NTLMv1 authentication exchanges, which are still enabled in some legacy Windows environments. Once recovered, credentials can be reused for lateral movement, privilege escalation, or unauthorized access to additional systems within a network.
Who is affected
Organizations still permitting NTLMv1 authentication are directly affected, particularly those with legacy systems or backward compatibility requirements.
Why CISOs should care
Weak authentication protocols undermine enterprise identity security, enabling rapid credential compromise and increasing the likelihood of lateral movement and domain-wide exposure.
3 practical actions
- Disable NTLMv1: Enforce modern authentication protocols and block legacy NTLMv1 usage.
- Monitor authentication traffic: Identify NTLMv1 negotiation attempts within the environment.
- Harden credential protections: Apply strong password policies and limit credential reuse across systems.