Kaspersky Lab has filed antitrust complaints against Microsoft with the European Commission and the German federal cartel office.
The software security company claims that Microsoft is abusing its market dominance to crowd out anti-virus software makers, pushing Windows 10 users toward its own Windows Defender software.
"These actions by Microsoft lead to a lower level of protection for users, a limitation on their right to choose, and financial losses both for users and security solutions manufacturers," Kaspersky said.
The European Commission confirmed it had received Kaspersky's complaint. Microsoft has not provided any comment yet.