Microsoft's built-in antivirus started blocking links to Google

The Microsoft Defender security service for Office 365 has begun mistakenly labeling ordinary links to Google's search engine as dangerous. When attempting to follow them, users see a threat warning, and system administrators receive notifications of a cyberattack.

Why did Google search suddenly become "unsafe"?

According to BleepingComputer, users of corporate systems are encountering a warning window that shows the text "Opening this website may be dangerous."

The error occurred due to an incorrect functioning of the Safe Links module within Microsoft Defender for Office 365. This tool rewrites incoming URLs in emails, Teams chats, and Office apps 365, and also checks them directly at click time. Since the tool fully changes the URL address, normal copying of the link into a browser does not help bypass the block.

Microsoft Defender for Office 365 Safe Links may block opening Google search links, identifying them as malware. In addition, administrators may receive appropriate notifications and incidents in the Microsoft Defender and Microsoft Sentinel portals as a result of these detections,

– commented the Microsoft company.

The glitch caused a false security classification. The developers have already launched the process of fixing this error.

We have found that an inaccurate security classification causes legitimate Google search URL addresses to be incorrectly identified as malicious, which leads Microsoft Defender for Office 365 Safe Links to block access to these links. We are working on correcting the false classification to eliminate the consequences,

– said a spokesperson for the developer.

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Systematic false activations of Microsoft technologies

Currently the company classifies the incident as an informational notice, which usually indicates a limited scope of the problem. However, this is not the first time the developer's protective algorithms confuse safe content with threats.

Last year, a failure in Exchange Online caused the machine learning model to mistakenly label emails from Gmail accounts as spam.

Another bug-prone system sent entirely legitimate correspondence to quarantine.

In February of this year, another issue in Exchange Online blocked sending and receiving emails, moving safe messages to a phishing quarantine.

Parallel to this incident, Microsoft specialists are addressing a large-scale outage in Microsoft 365 services, which caused authentication problems, delays in operation, and connection failures.