Windows 10 does disable some third-party security software, Microsoft has admitted, but because of compatibility – not competitive – issues.

Redmond is currently being investigated in the EU, Germany and Russia over alleged anti-competitive behavior because it bundles the Windows Defender security suite into its latest operating system. Kaspersky (and others) claim Microsoft is up to its Internet Explorer shenanigans again, but that’s not so, said the operating system giant.

“Microsoft’s application compatibility teams found that roughly 95 per cent of Windows 10 PCs had an antivirus application installed that was already compatible with Windows 10 Creators Update,” said Rob Lefferts, director of security in the Windows and Devices group.

“For the small number of applications that still needed updating, we built a feature just for AV apps that would prompt the customer to install a new version of their AV app right after the update completed. To do this, we first temporarily disabled some parts of the AV software when the update began.”

Lefferts claimed that Windows Defender is fine with other security software on a PC, but if that third-party code expires or becomes outdated then Redmond’s security software will kick in. He said Defender wouldn’t scan a system without the permission of the operator.

He also said that Microsoft works actively with third-party security firms to ensure compatibility, but is short on specifics. One of the key planks of Kaspersky’s case against Microsoft is that it cut compatibility testing times from two months to six days.

The antitrust case seeks to stoke fears that Microsoft is pulling the same trick with security software that it did with browsers. Redmond’s then-CEO Bill Gates was convinced the internet was a fad and missed the boat on browsers. They then locked Internet Explorer into the operating system to make up the lost ground – a decision that cost the company dearly in the long run, but still destroyed Netscape in the process.

Kaspersky is worried that Microsoft is trying the same trick, but – based on Lefferts' post – Redmond is ready to fight such claims. Windows 10 is naggy in a lot of regards (it seldom tires of saying how good Edge is), but proving it's anti-competitive will be a very big chasm to cross. ®