Linux.com: How to Harden GNU/Linux Against Local Intrusions

“So, you’ve set up parental filtering, only to discover that an
overachieving teenager has Googled a way around it. You’ve just
been the victim of a local intrusion. Preventing such an occurrence
on GNU/Linux requires a little knowledge and even less work. Here’s
how.

“A local intrusion occurs when a computer is ‘cracked’ by
someone with physical access to a computer. This can be done with
actual hacking techniques, or by exploiting built-in boot
(failsafe) modes that your computer’s operating system,
bootloaders, and BIOS contain…”

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