Forced Authentication

What the technique is

Adversaries may gather credential material by invoking or forcing a user to automatically provide authentication information through a mechanism in which they can intercept. The Server Message Block (SMB) protocol is commonly used in Windows networks for authentication and communication between systems for access to resources and file sharing. When a Windows system attempts to connect to an SMB resource it will automatically attempt to authenticate and send credential information for the current user to the remote system. This behavior is typical in enterprise environments so that users do not need to enter credentials to access network resources. Web Distributed Authoring and Versioning (WebDAV) is also typically used by Windows systems as a backup protocol when SMB is blocked or fails. WebDAV is an extension of HTTP and will typically operate over TCP ports 80 and 443. Adversaries may take advantage of this behavior to gain access to user account hashes through forced SMB/WebDAV authentication. An adversary can send an attachment to a user through spearphishing that contains a resource link to an external server controlled by the adversary (i.e. Template Injection), or place a specially crafted file on navigation path for privileged accounts (e.g..SCF file placed on desktop) or on a publicly accessible share to be accessed by victim(s). […]

What MITRE says you would watch

• AN0065

  Adversary stages a lure that references a remote resource (e.g., LNK/SCF/Office template). When the user opens/renders the file or a shell enumerates icons, the host automatically attempts SMB or WebDAV authentication to the attacker host. The chain is: (1) lure file is created or modified in a user-exposed location → (2) user or system accesses the lure → (3) host makes outbound NTLM (SMB 139/445 or WebDAV over 80/443) to an untrusted destination → (4) repeated attempts from multiple users/hosts or from privileged workstations.