Checking protection is on
The computer is protected by on-access scanning.
On-access scanning intercepts files as they are accessed, and grants access to only those that do not pose a threat to your computer or are authorized for use.
When on-access scanning is active, a blue shield is displayed in the system tray.
When on-access scanning is inactive, the shield is gray.
Note: The status of on-access scanning is also indicated in the Sophos Anti-Virus window under Status.
If your computer is on a network, on-access scanning has probably already been configured. However, if you want to change the settings, refer to Configuring scanning.
Turning protection on or off for the computer
If you turn protection off, Sophos Anti-Virus does not scan files that you access for threats.
Note: You need to be a member of the SophosAdministrator group to turn protection on or off for a computer.
On the Configure menu, click On-access scanning.
In the On-access scan settings for this computer dialog box, click the Scanning tab.
To turn on-access scanning on for the computer, select Enable on-access scanning for this computer, and click OK. The Sophos Anti-Virus system tray icon turns blue.
To turn on-access scanning off for the computer, deselect Enable on-access scanning for this computer, and click OK. The Sophos Anti-Virus system tray icon turns gray.
In the Sophos Anti-Virus window, the Status menu is updated.
Note: Sophos Anti-Virus retains the settings you make here, even after you restart the computer. If you have turned on-access scanning off, it remains inactive until you turn it on again.
Note: If you turn on-access protection off, you can still run on-demand scans of your computer.
Disclaimer: The images in this post were obtained through Google Images search, and their respective website locations should show up in the image text of this post. If not, I can provide you with the link. (Just covering my bum)