The term “not a virus” is used by antivirus software to indicate that a file does not match known malware signatures but still triggers a detection. This means the file is not automatically blocked or confirmed as a threat; the alert highlights something unusual, leaving the decision to the user. Alerts typically arise when software exhibits behavior associated with increased risk, despite lacking clear evidence of malicious intent. Malware is specifically designed to inflict harm, while files labeled “not a virus” may perform actions that raise security concerns but are not classified as harmful. Antivirus programs identify threats through signature detection and heuristic behavior-based detection. Legitimate programs, such as system utilities, download managers, and game cheats, can inadvertently trigger “not a virus” alerts. Common types of detections include adware, riskware, and potentially unwanted applications (PUA). The primary security risk of “not a virus” files is exposure rather than direct attacks, and privacy concerns often arise from data collection by these programs. If an antivirus detects “not a virus,” users should identify the file, review recent changes, compare detections, and decide whether to keep or remove it. To reduce unwanted alerts, users should download from official sources, use custom installation options, and remove unused software.