Adversaries may abuse a valid Kerberos ticket-granting ticket (TGT) or sniff network traffic to obtain a ticket-granting service (TGS) ticket that may be vulnerable to Brute Force.(Citation: Empire InvokeKerberoast Oct 2016)(Citation: AdSecurity Cracking Kerberos Dec 2015)
Service principal names (SPNs) are used to uniquely identify each instance of a Windows service. To enable authentication, Kerberos requires that SPNs be associated with at least one service logon account (an account specifically tasked with running a service(Citation: Microsoft Detecting Kerberoasting Feb 2018)).(Citation: Microsoft SPN)(Citation: Microsoft SetSPN)(Citation: SANS Attacking Kerberos Nov 2014)(Citation: Harmj0y Kerberoast Nov 2016)
Adversaries possessing a valid Kerberos ticket-granting ticket (TGT) may request one or more Kerberos ticket-granting service (TGS) service tickets for any SPN from a domain controller (DC).(Citation: Empire InvokeKerberoast Oct 2016)(Citation: AdSecurity Cracking Kerberos Dec 2015) Portions of these tickets may be encrypted with the RC4 algorithm, meaning the Kerberos 5 TGS-REP etype 23 hash of the service account associated with the SPN is used as the private key and is thus vulnerable to offline Brute Force attacks that may expose plaintext credentials.(Citation: AdSecurity Cracking Kerberos Dec 2015)(Citation: Empire InvokeKerberoast Oct 2016) (Citation: Harmj0y Kerberoast Nov 2016)
This same behavior could be executed using service tickets captured from network traffic.(Citation: AdSecurity Cracking Kerberos Dec 2015)
Cracked hashes may enable Persistence, Privilege Escalation, and Lateral Movement via access to Valid Accounts.(Citation: SANS Attacking Kerberos Nov 2014)
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