Security

The core security capabilities of Windows include: discretionary (need-to-know) protection for all shareable system objects (such as files, directories, processes, threads, and so forth), security auditing (for accountability of subjects, or users and the actions they initiate), password authentication at logon, and the prevention of one user from accessing uninitialized resources (such as free memory or disk space) that another user has deallocated.

Windows has two forms of access control over objects. The first form—discretionary access control—is the protection mechanism that most people think of when they think of operating system security. It's the method by which owners of objects (such as files or printers) grant or deny access to others. When users log in, they are given a set of security credentials, or a security context. When they attempt to access objects, their security context is compared to the access control list on the object they are trying to access to determine whether they have permission to perform the requested operation.

Privileged access control is necessary for those times when discretionary access control isn't enough. It's a method of ensuring that someone can get to protected objects if the owner isn't available.

Security pervades the interface of the Windows API. The Windows subsystem implements object-based security in the same way the operating system does; the Windows subsystem protects shared Windows objects from unauthorized access by placing Windows security descriptors on them. The first time an application tries to access a shared object, the Windows subsystem verifies the application's right to do so. If the security check succeeds, the Windows subsystem allows the application to proceed.