Raymond Chen, a seasoned Microsoft veteran with over three decades of experience, offers a clear piece of advice for users tempted to install multiple antivirus solutions: refrain from doing so. His insights emerged while assisting a colleague in diagnosing a complex failure on Windows 11 Enterprise PCs, where he observed a troubling interaction between two anti-malware programs. Each attempted to quarantine processes belonging to the other, leading to a cascade of conflicts.
“Installing two anti-malware programs on the same system is like hiring two different security companies to patrol your building,” Chen explains, illustrating the inherent chaos that can ensue. “If they don’t know about each other, each is going to think the other one is an intruder. If you’re lucky, their instructions are merely to report on suspicious activity.”
The antivirus conflicts on Windows 11 can go beyond quarantining each other
Chen further elaborates on the complications that arise with third-party anti-malware software, which may employ unsupported techniques such as “detouring system functions.” This can lead to significant performance degradation and other unforeseen issues. “These detours mean that calling a system function no longer does the system thing; instead, it calls into the anti-malware software, which might execute unrelated actions that can cause problems, such as system hangs,” he cautions.
The presence of multiple antivirus programs can create a perfect storm of technical difficulties, resulting in erratic Windows performance. Microsoft Defender, while resource-intensive at times, becomes even more burdensome when additional antivirus applications are introduced. Users may find themselves unable to pinpoint the source of their issues, often misattributing them to faulty Windows updates rather than conflicts between security programs.
In tests conducted by Windows Latest, many of these conflicts have been traced through the Event Viewer, although this can be a daunting task for the average user. The consensus remains clear: Microsoft advises against the use of third-party antivirus solutions.
Microsoft previously said Defender is enough for most users
In April 2026, Microsoft released a support document lauding Windows Defender (now rebranded as Microsoft Defender) as sufficient for the majority of users, suggesting that a third-party antivirus is unnecessary. This assertion was not without merit, as Defender has evolved significantly since its inception in the early 2000s.
Interestingly, Microsoft referred to Defender as the “best antivirus software for 2026,” a statement that was later retracted when the document was quietly removed shortly after its release. The abrupt deletion raised eyebrows, leading to speculation that the marketing implications may have influenced the decision.
Microsoft explains how Windows Defender is more than enough
In the now-archived document, Microsoft highlighted that Windows 11 comes equipped with a comprehensive “antivirus stack,” managed through the Windows Security app. This includes Defender Antivirus, SmartScreen, and Smart App Control, among other features designed to enhance security. The company emphasized that with default protections enabled, regular updates, and careful software downloads, Windows antivirus protection is typically adequate.
Moreover, Microsoft cautioned that running multiple real-time antivirus engines can lead to increased resource consumption and a higher likelihood of conflicts. This aligns with the experiences of many users, including those who have observed marked improvements in system performance and security incidents while relying solely on Defender. Independent testing organizations, such as AV-Test, have corroborated these findings, consistently ranking Microsoft Defender among the top antivirus solutions with impressive protection scores.
As users navigate the complexities of digital security, the question remains: are third-party solutions truly necessary, or can Microsoft Defender stand alone as a reliable guardian against threats? The conversation continues, inviting users to share their experiences and insights.
