Abusing a gMSA is relatively simple conceptually. First, get its password using a tool like Mimikatz or by querying it directly due to insecure configurations in Active Directory. Since gMSAs are service accounts, they’re usually relatively privileged, so you’ll usually be able to move laterally or escalate. Let’s walk through an example scenario.
Digest Authentication is a challenge/response protocol that was primarily used in Windows Server 2003 for LDAP and web-based authentication. It utilizes Hypertext Transfer Protocol (HTTP) and Simple Authentication Security Layer (SASL) exchanges to authenticate. At a high level, a client requests access to something, the authenticating server challenges the client, and the client responds to the challenge by encrypting its response with a key derived from the password.
When your web browser accesses a website, it needs to first translate the friendly URL (such as Netwrix.com) to the public server IP address of the server that hosts that website. This is known as a DNS lookup. Traditional DNS is unencrypted, unlike modern HTTPS web traffic that’s almost entirely secured via HTTPS these days.
A lot of attention gets paid to preventing pass-the-hash and pass-the-ticket attacks, but these tactics limit adversaries to what they can perform from the command line. Compromising a plaintext password gives an attacker unlimited access to an account — which can include access to web applications, VPN, email and more. One way to extract plaintext passwords is through Kerberoasting, but this brute-force technique takes a lot of time and patience.
DCShadow is a feature in the open-source tool mimikatz. In another blog post, we cover without detection once they’ve obtained admin credentials. But DCShadow can also enable an attacker to elevate their privileges. How can a Domain Admin elevate their access even higher? By obtaining admin rights in other forests. Leveraging SID History, an attacker can add administrative SIDs to their user account and obtain admin level rights in other trusted domains and forests.
