Set a firmware password
Most modern Macs support firmware passwords, but if you’re unsure yours does visit apple.co/2pOwb8l to check whether your model is compatible.
Restart your Mac holding Command-R to start up in macOS Recovery. Once that loads, click Continue on the language selection screen if it appears. From the menu bar, choose ‘Utilities > Firmware Password Utility’.
In the new window that opens, click ‘Turn On Firmware Password’. You’ll be prompted to enter your password twice, the second to verify that you entered it correctly the first time. Make sure this is different to your user account’s password and note it down in a safe place. Click ‘Set Password’ when you’re ready.
Restart the Mac. You will be able to log in as normal. However, from now on, if you or anyone else wants to start up from a different drive, enter single-user mode or access macOS Recovery, the firmware password must be entered first. Other tab. Alternatively, choose to limit applications in the Apps tab to only those you approve.
When it comes to browsing the web, although you can block individual websites, your kids may be able to circumvent restrictions by visiting a web proxy — a website designed to bypass controls like these, which will fetch the website for them. Keep a close eye on their account logs; if you find they’ve been visiting such sites, add them to the banned list.
Certain websites, such as Pirate Bay, maintain mirrors — in other words, multiple copies of the same web page at different locations around the internet. For this reason, while one mirror such as thepiratebay.org may be on the blocked list, another such as
pirateproxy.cc may still load. Again, watch your child’s web activity closely and add mirrors of sites to the block list as necessary.