Conventional disk scanner Conventional disk scanners scan contents of files, directories, and disks for any files or boot sectors that may contain viruses based on the current virus definitions. They may be run manually, but they can also be programmed to run at specific intervals. They can be used for preventive maintenance or act only when a virus is suspected. Memory-resident scanner Memory-resident antivirus software runs in the background, automatically scanning for viruses using different triggers. It is usually configured to scan automatically as the computer downloads files, runs disks or programs, or shuts down. Behavior-based detection Behavior-based detection runs in the background and looks for suspicious activities or virus-like behavior. It looks for common traps such as writing to hard disk boot sectors, attempting to format the hard drive, or writing to existing program files. Startup antivirus software A startup antivirus software is designed to scan for viruses every time the computer is started. It does a quick scan on critical system files and disk boot sectors instead of a full disk scan. Inoculation Inoculation software looks for the changes that the viruses have made to files and boot sectors instead of looking for the viruses themselves. It takes a snapshot of the clean system information from each boot sector, storing it to re-examine the files to see if anything has changed. It informs the user when changes have been made. It can detect new viruses without the need for updating the virus definition files, but it tends to generate false positives. | 
