Detect Forced SMB/WebDAV Authentication via lure files and outbound NTLM

Technique Detected:  Forced Authentication | T1187

ID: DET0022
Domains: Enterprise
Analytics: AN0065
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

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.

Log Sources
Data Component Name Channel
File Creation (DC0039) WinEventLog:Sysmon EventCode=11
File Modification (DC0061) WinEventLog:Security EventCode=4663
Network Traffic Content (DC0085) NSM:Flow HTTP/WebDAV requests that contain NTLMSSP or PROPFIND/MOVE/OPTIONS with Authorization: NTLM
Network Traffic Flow (DC0078) NSM:Flow Outbound connections to TCP 139,445 and HTTP/HTTPS to WebDAV endpoints from workstation subnets
Mutable Elements
Field Description
UserLocations Folders where lures are most effective (Desktop, Public, Downloads, Temp, Cache, Start Menu, Startup). Adjust to enterprise layout.
LureExtensions File types commonly abused (.lnk, .scf, .url, .doc/.xls/.ppt/.pdf/.html). Extend for your tooling and languages.
UntrustedCIDR/DNS Org-specific list of external/unknown networks or domains; used to suppress sanctioned file servers and WebDAV gateways.
TimeWindow Correlation horizon (e.g., 15–30 minutes) between file access and outbound NTLM attempt.
WorkstationZones Asset/zone tags that distinguish workstations from servers; helps flag workstation→workstation SMB, which is often abnormal.
OfficeTemplatePaths Paths to Office templates to catch template injection references and abnormal loads.