Guest vs Null session on Windows

This blog post explains the differences between Guest authentication and Null/Anonymous sessions in Windows/Active Directory, showing how guest fallback and anonymous permissions can enable SMB access and domain enumeration (e.g., via SAMR) even without valid credentials. It demonstrates practical behaviors observed in traffic captures and tools like NetExec, outlines the role of the “Pre-Windows 2000 Compatible Access” and “Anonymous Logon” groups, and concludes with mitigation advice to disable guest accounts and restrict anonymous permissions.