## 6.6.2 Filter Types

Within the body of the filter you can then define one of the following interceptor types for the filter:

- `before` - Executed before the action. Can return false to indicate all future filters and the action should not execute
- `after` - Executed after an action. Takes a first argument as the view model
- `afterView` - Executed after view rendering

For example to fulfill the common authentication use case you could define a filter as follows:

    class SecurityFilters {
       def filters = {
           loginCheck(controller:'*', action:'*') {
               before = {
                  if(!session.user && !actionName.equals('login')) {
                      redirect(action:'login')
                      return false
                   }
               }       }
       }
    }

Here the `loginCheck` filter uses a `before` interceptor to execute a block of code that checks if a user is in the session and if not redirects to the login action. Note how returning false ensure that the action itself is not executed.