Microsoft Learn

Understanding Access Control in Windows

Access control is a fundamental security mechanism in Windows that governs which users and processes can perform specific actions on system resources. This includes files, folders, registry keys, network shares, and more. By implementing robust access control, Windows ensures that only authorized entities can interact with sensitive data and system components.

The primary mechanism for access control in Windows is the Access Control List (ACL). Each securable object in Windows has an associated ACL, which contains a set of Access Control Entries (ACEs). Each ACE specifies a security principal (like a user or group) and the type of access (allow or deny) for a particular permission.

Key Concepts:

• Security Principals: Users, groups, and service accounts that are granted or denied access.
• Permissions: Specific actions that can be performed on an object (e.g., Read, Write, Execute, Delete).
• Access Control List (ACL): A collection of ACEs associated with an object.
• Access Control Entry (ACE): A single entry within an ACL defining access for a specific security principal.
• Discretionary Access Control List (DACL): The part of the ACL that grants or denies access.
• System Access Control List (SACL): The part of the ACL that specifies which access attempts are audited.

Working with ACLs

Administrators can manage ACLs using various tools, including File Explorer (Properties > Security tab), the command line (icacls.exe), and PowerShell cmdlets. Understanding how to effectively configure permissions is crucial for maintaining a secure Windows environment.

Common Permissions for Files and Folders:

• Full Control: Allows all actions, including changing permissions and taking ownership.
• Modify: Allows reading, writing, executing, and deleting files and subfolders.
• Read & Execute: Allows viewing file contents and running executable files.
• List Folder Contents: Allows viewing the names of files and subfolders.
• Read: Allows viewing file contents and folder structure.
• Write: Allows creating new files and folders, and writing to existing files.

Example: Using icacls Command

To grant read and execute permissions to a specific user for a folder named "SecureData":

Explanation:

• "C:\SecureData": The target folder.
• /grant Users:(OI)(CI)RX: Grants permissions to the "Users" group.
• (OI): Object Inherit - ACE applies to files.
• (CI): Container Inherit - ACE applies to subfolders.
• RX: Read & Execute permissions.

Inheritance and Propagation

Permissions can be inherited from parent objects (folders) to child objects (files and subfolders). This simplifies permission management, as you don't need to set permissions individually for every item. You can control whether permissions are inherited and how they propagate down the folder structure.

Effective Permissions

The effective permissions for a user on a resource are the combined result of permissions granted directly to the user, permissions granted to groups the user belongs to, and inherited permissions. Deny ACEs take precedence over Allow ACEs.

Resources for Further Learning

Dive deeper into the intricacies of Windows access control with these official Microsoft resources: