Those of you with on-premises Active Directory (AD) need to be aware of a new way to abuse Kerberos in your network. KrbRelayUp is a bundle of tools that streamlines the use of some features in Rubeus, KrbRelay, SCMUACBypass, PowerMad/SharpMad, Whisker, and ADCSPwn. Attackers use the toolset to impersonate an administrator via resource-based constrained delegation and execute code on a device’s system account.
Pure Azure AD environments are safe from this attack, but hybrid AD networks with both on-premises AD and Azure AD will be at risk. If an attacker compromises an Azure virtual machine that is synchronized with on-premises active directory, the attacker will gain system privileges on the virtual machine and be able to make more advances inside the network.