A custom expression is one that you create within the policy. When you create an expression, you configure the parameters for the expression.
You can also create custom client security expressions to refer to commonly used client security strings. This eases the process of configuring preauthentication policies and also in maintaining the configured expressions.
For example, you want to create a custom client security expression for Symantec AntiVirus 10 and make sure that the virus definitions are no more than three days old. Create a new policy and then configure the expression to specify the virus definitions.
The following procedure shows how to create a client security policy in a preauthentication policy. You can use the same steps in a session policy.
When you configure a custom expression, it is added to the Expression box in the policy dialog box.