Multiple Invalid Users Failing To Authenticate From Host Using Ntlm

Multiple Invalid Users Failing To Authenticate From Host Using Ntlm

Description

The following analytic identifies one source endpoint failing to authenticate with multiple invalid users using the NTLM protocol. This behavior could represent an adversary performing a Password Spraying attack against an Active Directory environment using NTLM to obtain initial access or elevate privileges. As attackers progress in a breach, mistakes will be made. In certain scenarios, adversaries may execute a password spraying attack using an invalid list of users. Event 4776 is generated on the computer that is authoritative for the provided credentials. For domain accounts, the domain controller is authoritative. For local accounts, the local computer is authoritative. Error code 0xC0000064 stands for The username you typed does not exist (the attempted user is a legitimate domain user).\ The detection calculates the standard deviation for each host and leverages the 3-sigma statistical rule to identify an unusual number of users. To customize this analytic, users can try different combinations of the bucket span time and the calculation of the upperBound field. This logic can be used for real time security monitoring as well as threat hunting exercises.\ This detection will only trigger on domain controllers, not on member servers or workstations.\ The analytics returned fields allow analysts to investigate the event further by providing fields like source workstation name and attempted user accounts.

   Help

Multiple Invalid Users Failing To Authenticate From Host Using Ntlm Help

To successfully implement this search, you need to be ingesting Domain Controller events. The Advanced Security Audit policy setting Audit Credential Validation' withinAccount Logon` needs to be enabled.

   Search

Open in Search