Silver Ticket Used for SMB Service Authentication
This rule detects the use of a Silver Ticket for SMB service authentication. A Silver Ticket is a forged Kerberos service ticket that allows an attacker to authenticate to a specific service (like SMB) on a specific server without needing to interact with the Domain Controller. The rule looks for TCP traffic on port 445 (SMB) containing both 'NTLMSSP' and 'KRB5' content, indicating a Kerberos authentication attempt that might be a Silver Ticket. A threshold is applied to prevent excessive alerts.
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