1. Make sure you have a good inventory of organizational IT assets, both hardware and software.
2. Remove end-user administrative access to their systems.
3. Ensure a vulnerability management platform is employed.
4. Create standard device images that are approved for use in the organization.
5. Deploy a white-listing capability based on your standard images.
White listing allows only approved software to run on specified devices. There are several solutions available, from built-in operating system components, such as AppLocker on Windows, to various third-party solutions from Bit9, Faronics, and McAfee, among many others.
Zero-day vulnerabilities will be a reality for as long as we use software as a productivity tool in the workplace (so add zero-days to death and taxes). If you are not controlling the end-user work environment, then you are leaving your organizational assets open to compromise from the unknown cyber attacks of tomorrow.