Some essential features of Spring Security include:

Supports authentication and authorization in a flexible and comprehensive manner.

Detection and prevention of attacks including session fixation, clickjacking, cross-site request forgery, etc.

Integrate with Servlet API.

Offers optional integration with Spring Web MVC (Model-View-Controller).

Java Authentication and Authorization Service (JAAS) is used for authentication purposes.

Allows Single Sign-On so that users can access multiple applications with just one account (username and password) 

Authorization

Single sign-on

Software Localization

Remember-me

LDAP (Lightweight Directory Access Protocol)

JAAS (Java Authentication and Authorization Service) LoginModule

Web Form Authentication

Digest Access Authentication

HTTP Authorization

Basic Access Authentication