After U.S. ban, Kaspersky's American customers were automatically migrated to UltraAV antivirus, in some cases without the customers' knowledge.

Last week, users of Kaspersky anti-virus software found that the software had been uninstalled from their computers and that UltraAV's anti-virus had been installed in its place. The users had not consented to or initiated any of it.

The Russian cybersecurity company says it's been notifying users of the change and is aiming for a smooth transition of software.