Black flag down: Microsoft has closed an activation loophole that was widely used by software pirates to run Windows and Office without a legitimate license. The group behind the activation tool has confirmed that the method no longer works following the November 2025 Patch Tuesday update.
Known as the KMS38 activator, the open-source tool was created by a group called Massgrave, where MAS stands for Microsoft Activation Scripts. It was widely regarded as one of the easiest and safest ways to activate Windows and Office without paying, allowing users to install all official updates just like any legitimately licensed copy.
Following the latest update, however, PCs activated with the tool are losing their activation, with users now seeing messages urging them to purchase a legitimate license from Microsoft or its authorized resellers. Legal Windows 11 licenses can be found online for as low as $10, while Office 2021 Pro is available for around $39.
KMS38 has circulated online for years across software forums, piracy websites, and GitHub mirrors, attracting a large community of both tech-savvy users and newcomers. Curiously, the download is actually hosted on two Microsoft-owned platforms: Azure DevOps and GitHub. Massgrave's developers also maintain a self-hosted Git repository and a website offering step-by-step activation guides.
While some argue that blocking the KMS38 activation method is a step toward protecting users from malware, others counter that KMS38 is an open-source tool that anyone can inspect for malicious code. Several reputable tech outlets, including ZDNet, have tested the activation method and reported that it works exactly as advertised.
Massgrave's latest changelog notes that the main KMS activation option has been removed from the tool following Microsoft's block. The developers are now urging users to switch to the HWID (Hardware ID) or TSforge activation methods, which still function as expected. They also say they're hopeful they can circumvent the block in the future.
This crackdown on unofficial activation methods comes just weeks after Microsoft tightened the Windows 11 installation process by blocking all known methods of setting up the OS without a Microsoft account. The update now makes it impossible to install Windows 11 offline using a local account.
Windows and Office piracy has long been a major challenge for Microsoft, though the company has historically taken a relatively relaxed stance on the issue.
Bill Gates even once admitted that piracy helped supercharge Windows adoption and cement its status as the dominant desktop operating system. But Microsoft's recent actions suggest that Redmond may finally be shifting away from its formerly lenient attitude toward piracy.
Your pirated copy of Windows might have just stopped working
