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.
Since actual hacking methods are very uncommon due to the level of expertise they require, we'll limit our discussion to hardening the built-in boot modes. These modes are in place mainly to recover or repair a computer after a system failure or forgotten password. Because these necessary failsafes exist, physical security is the weakest layer of computer security, no matter what operating system is being used. You need to be logged in as root to perform these steps, with the exception of the BIOS changes.
By Joe Bolin at Linux.com
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