Windows Profile Directory Permissions

TL;DR

No, you cannot assume a Windows profile directory is not writable by other users. While permissions are set to restrict access, they can be bypassed or modified. You need to actively verify and enforce restrictions.

Solution Guide

1. Understand Default Permissions: By default, user profiles have permissions that allow the owner (the user) full control. Other users typically have limited access – read & execute, list folder contents. However, this isn’t a guarantee of security.
   • Administrators generally have full control over all profiles.
   • The ‘Users’ group may have some level of access depending on system configuration.
2. Check Current Permissions: Verify the permissions on a specific profile directory.
   1. Open File Explorer and navigate to C:Users<username> (replace <username> with the actual username).
   2. Right-click the user’s folder and select ‘Properties’.
   3. Go to the ‘Security’ tab.
   4. Review the listed users and groups, and their assigned permissions. Pay close attention to ‘Write’ access.
3. Using icacls (Command Line): A more detailed way to view permissions is using the command line.

   icacls "C:Users<username>"

   This will output a list of Access Control Lists (ACLs) for the directory, showing who has what access. Look for entries with ‘W’ (Write) permission.

4. Potential Bypass Methods: Be aware of ways permissions can be circumvented.
   • Administrator Accounts: Any user with administrator privileges can modify profile directories.
   • Malware/Viruses: Malware can alter permissions to gain access.
   • Group Policy Settings: Incorrectly configured Group Policy settings could grant unintended access.
   • File System Vulnerabilities: Though rare, vulnerabilities in the file system itself could be exploited.
5. Enforce Restrictions (Recommended): Don’t rely on default permissions alone.
   1. Principle of Least Privilege: Grant users only the minimum necessary access rights. Avoid giving standard users write access to other user profiles unless absolutely required.
   2. Group Policy: Use Group Policy to centrally manage profile directory permissions. This is especially important in a domain environment.
      • Configure folder redirection to store data on a network share with appropriate security settings.
      • Restrict access to specific folders within profiles using GPO-based file system ACLs.
   3. Regular Auditing: Regularly audit profile directory permissions to identify and correct any misconfigurations.

      icacls "C:Users*" /inheritance:d

      This command removes inherited permissions from all user folders. Use with caution, as it can disrupt functionality if not carefully planned.

6. Cyber security Considerations: Profile directories often contain sensitive data (documents, browser history, saved passwords). Protecting these directories is crucial for overall system cyber security.
   • Implement strong password policies.
   • Use full disk encryption (e.g., BitLocker) to protect the entire drive, including profile directories.
   • Employ endpoint detection and response (EDR) solutions to detect and prevent malicious activity.