In Xubuntu 12.10, session is no longer locked when you Suspend, so it doesn't ask for a password on wakeup. To solve this, we need to make changes to xfce4-session and xfce4-power-manager.

Using Terminal Commands

Run the following commands in terminal (press Ctrl + Alt + T) to make changes to both xfce4-session and xfce4-power-manager to lock the session when you Suspend:

xfconf-query -c xfce4-session -p /shutdown/LockScreen -s true

xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/lock-screen-suspend-hibernate -s true

Alternatively — Using GUI

We need to make changes in both Session and Startup as well as Xfce Power Manager.

You would find both of them to be available under Settings Manager. Right Click on your Desktop and navigate through Applications → Settings → Settings Manager to open it.

1. Session and Startup

   
   
   

   Open Session and Startup → navigate to the Advanced Tab → put a checkmark next to Lock screen before sleep.

   
   
   

   




2. Xfce Power Manager

   
   
   

   Open Xfce Power Manager → click on Extended in the sidebar → put a checkmark next to Lock screen when going for suspend/hibernate.

   
   
   

   

Once you have made the changes, you should be asked for the password when you wakeup after Suspend.

Acknowledgement: Information and images for Session and Startup and Xfce Power Manager courtesy this Ubuntu Forums Thread.