Defender Antivirus is Microsoft’s built-in antivirus engine for Windows devices. It provides real-time malware detection, scheduled scanning, cloud-assisted protection, and status reporting that help organizations maintain a basic security baseline without installing a separate product.
It matters because endpoint protection is both a control and a source of telemetry. If Defender Antivirus is disabled, tampered with, or misconfigured, a device can become easier to compromise and harder to monitor. Attackers often try to weaken or bypass antivirus before dropping payloads or running living-off-the-land tools, while defenders use policy, health checks, and centralized management to confirm that protection is actually active. False status alerts can also cause confusion, so administrators should verify Defender’s state through more than one management view when warnings conflict with expected behavior.