Antivirus applications traditionally conducted signature-based checking, wherever each virus and malicious program had a certain electronic signature or rule structure that the program recognized. When a disease scan was started, the antivirus might evaluate the data on a pc using its database of known signatures to get matches. In case a match was noticed, the antivirus flagged the file as a possible threat and took action according to their set instructions. While efficient against known worms, this approach fought against new, as yet not known, or modified malware types, which did not even have a signature in the antivirus database. This issue led to the progress of heuristic-based detection, a more practical approach that allows antivirus applications to analyze the behavior and design of documents to identify potentially detrimental actions or signal patterns, even when the file itself is unknown.

The process of a virus check generally begins with an intensive examination of the system's memory and active processes. This task guarantees that any presently operating detrimental computer software is discovered and ended before it can interfere with the scanning process or further injury the system. After the productive techniques are checked, the antivirus techniques onto reading documents saved on the hard disk drive, focusing first on critical parts such as the functioning system's core files, boot areas, program registries, and frequently targeted folders. Modern antivirus programs provide customers the choice to decide on between rapid runs, which check always high-risk places where spyware is typically found, and full scans, which meticulously examine every check url  and folder on the device. Although complete scans give more detailed defense, they also eat more time and program resources, which is why many consumers routine them all through off-hours or intervals of minimal pc usage.

Another essential part of virus checking is the capability to check detachable storage devices such as for example USB thumb drives, external hard disk drives, memory cards, and even smartphones when linked to a computer. Malware can simply transfer from an infected USB system to a clean pc and vice versa, rendering it essential to scan any external press before accessing its contents. Some antivirus answers immediately initiate a scan each time a new unit is linked, providing one more coating of security against such threats. Furthermore, several virus scanners are now capable of checking compressed files like ZIP and RAR archives. Spyware is frequently hidden within these files to evade recognition, so scanning archived files has become a essential function for modern antivirus programs.