Microsoft’s anti-virus efforts have hit the news recently, following the spread of the massive WannaCry malware and an EU antitrust complaint from anti-virus company Kaspersky. The software giant is now detailing its anti-virus work, attempting to diffuse complaints over its anti-virus partner work and the security of Windows itself. Kaspersky has accused Microsoft of disabling its anti-virus software on Windows PCs, and using its dominance to “fiercely promote” its own Windows Defender software.

Rob Lefferts, director of program management for Windows enterprise and security, lays out Microsoft’s defense in more than 1,300 words in a sprawling company blog post today. While Lefferts doesn’t address Kaspersky directly, he does defend Microsoft’s bundling of its Windows Defender anti-virus software, noting that Microsoft "built Windows Defender Antivirus to make a promise to our customers that every Windows 10 device ALWAYS has protection from viruses and malware.”

Microsoft admits it does disable old anti-virus software

Lefferts also explains Microsoft’s reasoning for disabling third-party anti-virus software. While Microsoft claims 95 percent of Windows 10 PCs had compatible anti-virus protection for the recent Windows 10 Creators Update, a small number still needed updating. Windows 10 prompts to install a new version of anti-virus from third parties like Kaspersky after an update, but it disables the old version if it’s not compatible. “We first temporarily disabled some parts of the AV software when the update began,” explains Lefferts. “We did this work in partnership with the AV partner to specify which versions of their software are compatible and where to direct customers after updating.”

Kaspersky has also accused Microsoft of not providing enough time to fully test its latest versions of Windows 10 to ensure existing software is compatible. “We also know that Window customers value choice and that is why we actively engage with and support a community of over 80 independent software vendors through the Microsoft Virus Initiative (MVI) program,” says Lefferts. “We’ve worked closely with AV partners to identify changes, provide early builds through the Windows Insider Program and other testing environments, and provide technical guidance through our MVI program.” Microsoft also claims its Insider Program provides anti-virus partners with even greater insight into the Windows developer process than ever before.

While Microsoft doesn’t address Kaspersky directly, the company has been trying to reach out to officials at the anti-virus company to arrange a meeting and deal with the concerns ahead of an EU antitrust complaint that was filed recently. It’s clear there’s a lack of communication between the two companies. Microsoft defends itself simply by claiming it believes in "always on" anti-virus protection, as a safeguard against third-party subscription issues or older software. Kaspersky obviously disagrees, but it's now leaving it up to the European commission to decide whether there are enough issues here to even consider a case against Microsoft.