i would like to prevent these OS's from logging in to my SSLVPN portal
how can this be done?
You could set a browser restriction in your realm or role
Restrictions - Browser *MAC* Deny
Create a Host Checker policy based on OS. Put values in it for Windows, such as choosing to look for WindowsXP SP2. Do not put any values in the Mac or LInux tabs.
Require and enforce the policy at the User Realm / (realm) / Role Mapping rules
do the following custom expression and add that to the top of the roles that get assigned to your realm. do not assign these users any roles and do the stop rule as well this should take care of them
userAgent = '*Linux*' OR userAgent = '*MAC*'