Overview
- Microsoft, in a document dated April 9, said Defender covers everyday risks for typical Windows 11 setups that stay updated and use default protections.
- Recent testing backs the claim, with AV-Test awarding full marks and AV-Comparatives measuring protection between 98.5% and 100%.
- Security outlets reported three Defender zero‑day flaws in April, with one fixed and two still exploitable, including bugs that let attackers gain system rights or disable the scanner.
- Microsoft points to valid reasons to add third‑party tools, such as centralized control for businesses or home suites with parental controls, identity monitoring, or a VPN.
- The company and reviewers advise using only one real‑time antivirus, since running multiple scanners increases CPU and RAM use and can cause conflicts with Windows protections.