Operating System is the interface between computer hardware and the user. It's important to secure the OS in each system because *one insecure OS can lead to a whole network being compromised*. There are many types of operating systems, and they all share similar security hardening practices. Some OS hardening tasks are performed at **regular intervals**, like *updates, backups, and keeping an up-to-date list of devices and authorised users*. Other tasks are **performed only once** as part of preliminary safety measures. One example would be *configuring* a device setting to fit a *secure encryption standard*. ### Patch Update A patch update is a software and operating system update that *addresses security vulnerabilities* within a program or product. With patch updates, the OS should be upgraded to its latest software version. Sometimes patches are released to *fix a security vulnerability* in the software. As soon as OS vendors publish a patch and the vulnerability fix, **malicious actors know exactly where the vulnerability is** in systems running the out-of-date OS. This is why it's important for organisations to run patch updates as soon as they are released.