How to find this setting:
Protection Settings > Viruses & Spyware Controls
Your security software analyzes basic information about every file that you open, save, or download. For threats like viruses, it attempts to remove the threat from the infected file. If unable to remove the threat, it deletes the infected file along with the threat.
Mark the Scan
for threats when opening, saving, or downloading
files checkbox to detect and eliminate security
threats automatically.
Important warnings appear when your security software deals with a threat.
Mark
the Display a warning after detecting viruses,
spyware, or suspicious behavior checkbox to make sure
you see these messages.
Some threats may remain hidden or dormant on the computer for a long time before they act. Your security software can find and stop such threats before they start to cause trouble.
Mark
the Conduct a scheduled scan of the
computer checkbox to check your files and settings
for hidden threats.
Use the lists under the checkbox to select when the scan should begin. Choose a time when you would normally not use the computer very much after switching it on, like lunchtime on a Friday.
Your security software can not only search for threats in files and settings, but also check for suspicious behavior on your computer.
Mark the Check
if programs try to make unauthorized changes to system settings
that could threaten your security checkbox to block
suspicious changes. Such changes can result in Web browser
hijackings, unwanted but unremovable Web browser toolbars, or
reduced computer performance, among other problems.
Mark
the Prevent programs on portable drives from launching
automatically checkbox to block programs that try to
start running without your permission when you plug a USB drive
into the computer. Flash memory or other portable USB drives rarely
include certain kinds of programs that launch automatically, so
they usually represent a threat if found.
If you have strong concerns about your security, then you can take even stronger measures against threats.
Mark the Check
compressed files, such as ZIP files, during real-time
scans checkbox to check files reduced in size
through data compression techniques. Such files commonly end with
the ZIP or RAR extension and require a specific program to
"unpack," "unzip," or "decompress" the contents.
Mark
the Automatically delete files that show any signs of
a threat checkbox to get rid any file that might
cause trouble. This aggressive response could remove some harmless
files along with the unsafe ones, so consider using this protection
only when receiving files or installing programs that seem
risky.