Keep any software that cannot be removed from the system up to date.
Install all operating system security patches and software updates in a timely manner.
Operating system and software updates do have the potential to cause unforeseen problems. Thoroughly test all updates in a staging environment prior to production.
Monitor security-related mailing lists and news feeds, and consider following security experts on social media. The sooner you know about operating system or software vulnerabilities, the sooner you can take action to minimize the exposure while waiting for and testing the appropriate patches.