Microsoft say the update required to fix a security breach in its Internet Explorer computer software is now available to users.
The company discovered the problem last week, which if not fixed, could enable cyber-criminals to hack into users' computers remotely and take control of them.
Microsoft's national technology officer Brett Roberts says if users have automatic updates their computer has probably already been fixed.
But Mr Roberts says the emergency patch can also be installed manually if users go to the Microsoft website and follow instructions from there.
