Microsoft introduced at present that it was pressured to disable a key element of its Home windows app installer applied sciences as a result of it detected a number of cases of financially motivated risk actors utilizing these applied sciences to distribute malware. It additionally labored with Certificates Authorities to revoke the abused code-signing certificates that had been subverted to ship malware.
“Since mid-November 2023, Microsoft Risk Intelligence has noticed risk actors, together with financially motivated actors, using the App Installer to distribute malware,” the software program big defined. “Along with guaranteeing that clients are protected against noticed attacker exercise, Microsoft investigated the usage of App Installer in these assaults. In response to this exercise, Microsoft has disabled the [App Installer] protocol handler by default.”
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The App Installer is utilized by builders to put in a packaged Microsoft Retailer app in MSIX format from the net, a course of that was described as “side-loading” as a result of it bypasses the Retailer. However this episode casts doubt on whether or not Microsoft can assure that packaged apps put in from outdoors its Retailer can ever be thought of protected: As Microsoft notes, the hackers that attacked the App Installer protocol had been capable of impersonate legit software program installers that had been indistinguishable from the true factor.
What this implies in sensible phrases is that it’s now not potential to put in packaged Home windows apps from the net. As a substitute, customers might want to obtain the app bundle earlier than putting in it, which Microsoft says will give regionally put in antivirus and anti-malware providers an opportunity to check their integrity. Microsoft says that its Defender-based services and products have been up to date to handle this want, together with dealing with post-compromise situations.
“We are going to proceed to observe future malicious exercise and make ongoing enhancements to stop fraud, phishing, and a variety of different persistent threats,” the Microsoft Safety Response group guarantees. “Microsoft will stay vigilant as attackers proceed evolving their methods.”