Kerberos Pre-Auth Failures by Host

The
Kerberos Pre-Auth Failures by Host
alert indicates that several user accounts on the same device failed to authenticate a suspicious number of times in a 10-minute window, in what may be a password-spraying attack.

Synopsis

10 minutes
7 days
14 days
10 minutes
Any of the following:
  • Palo Alto Networks firewall traffic logs with Palo Alto Networks Firewall EAL logs
  • Windows event collector logs
Severity
Medium

Description

The host failed an unusual number of Kerberos pre-authentications (TGT requests) from at least three users when compared to its baseline from the previous 14 days.
This can indicate a password-spraying attack.

Attacker's Goals

The attacker is attempting to gain an initial foothold in the domain using a list of valid users and a guessed password.

Investigative Actions

  • Verify whether the host that generated the alert is normally used by many users (for example, a terminal server).
  • Verify any later authentication success for the user accounts referenced by the alert, as these can indicate the attacker managed to guess the credentials.

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