Kerberos- besides having three heads and guarding the gates of hell- protects services on Microsoft Windows Domains. Its use is increasing due to the growing number of attacks targeting NTLM authentication. Attacking Kerberos to access Windows resources represents the next generation of attacks on Windows authentication.In this talk Tim will discuss his research on new attacks against Kerberos- including a way to attack the credentials of a remote service without sending traffic to the service as well as rewriting tickets to access systems.He will also examine potential countermeasures against Kerberos attacks- with suggestions for mitigating the most common weaknesses in Windows Kerberos deployments.