Boot scans, also called shoe scans or pre-boot virus scans, are advanced tools that antimalware software employs to find and eliminate malware that may not have been detected by traditional scanning programs. This type of scan can be set to run on a regular basis or manually invoked by the user whenever they suspect that their computer is infected. A lot of antivirus programs let users select the sensitivity of the boot scan, as well as what actions should be taken in the event of a threat being detected.
The reason why a boot scan is effective is because it allows the antimalware program detect files that are in use by the operating system. These kinds of files can’t be deleted since they are constantly accessed by the OS and will return an Access Denied error when attempts are made to remove them. The boot scan will discover these files and allow the antivirus software to delete them before the OS can begin using them.
The time required for the boot scan can vary depending on a variety of factors, including the speed of the CPU, how many system files are being scrutinized and whether or not the computer is being used during the scanning process (thus changing the status of the files). This type of scan can take much longer than a typical anti-virus scan due to the thoroughness of the process.