A virus detection method for use in a computer system that contains at least one object that may potentially become infected with a computer virus. The method has steps of providing a database for storing information that is descriptive of a state of the object as it existed at a point in the past. For an object that is indicated as having a current state that is described by the stored information, another step programmatically examines the object for a presence of a computer virus while assuming that the current state of the object is the same as the state of the object as it existed at the point in the past. The the database stores additional information, beyond what is necessary to determine simply whether or not a particular object, such as a file, has changed. The additional information is employed to achieve a more rapid virus scan, even when the list of viruses being scanned for has changed since a previous scan.