This parameter controls what UNIX permission bits will be set when a Windows NT client is manipulating the UNIX permission on a directory using the native NT security dialog box. This parameter is applied as a mask (AND'ed with) to the incoming permission bits, thus resetting any bits not in this mask. Make sure not to mix up this parameter with , which works similar like this one but uses logical OR instead of AND. Essentially, zero bits in this mask are a set of bits that will always be set to zero. Essentially, all bits set to zero in this mask will result in setting to zero the corresponding bits on the file permissions regardless of the previous status of this bits on the file. If not set explicitly this parameter is set to 0777 meaning a user is allowed to set all the user/group/world permissions on a directory. Note that users who can access the Samba server through other means can easily bypass this restriction, so it is primarily useful for standalone "appliance" systems. Administrators of most normal systems will probably want to leave it as the default of 0777. force directory security mode security mask force security mode 0777 0700