When most people think of computer security, the images are usually of young crackers sitting in a dark bedroom, attack dialling the corporate giants and defence installations of the USA, ala War Games and the Cuckoo's Egg.
The truth of the matter is somewhat different, with various industry surveys estimating the level of security breaches by 'internal sources' as being between 75 and 90%.
While it is virtually impossible to guarantee a 100% secure computer system (short of turning the computer off, encasing it in concrete and employing the SAS to guard it on a 24 hour basis), there are a number of steps you can take to ensure that your computer is physically secure.
The weak points for any Linux box are typically:
Any modern BIOS will allow you to select the primary drive to boot from. By selecting C: then A: over the (typically) default settings of A: then C:, you can ensure that an attacker can not forcibly boot the system from their own customised boot disk.
If you ever need to boot from a floppy, reverse the BIOS boot options to boot from A: then C:, boot from the floppy, and then when you are sure you have finished working from a boot floppy, reinstate the original BIOS boot option.
To ensure that an attacker does not reconfigure the BIOS to allow them to boot from a floppy, enable the BIOS password system to protect BIOS configuration.
BIOS passwords can usually be selected between three states:
With some Linux distributions, attackers can get root access at the LILO prompt stage with either of the following commands that put Linux in single-user mode:
LILO: linux single LILO: linux 1
This can be prevented by either:
This forces the user to enter the password if parameters (such as single have been specified on the command line.
You can also add password protection to specific images, such as DOS partitions from which a user could run Norton Disk Editor or some other nefarious disk editing tool.
All of the measures above are useless if someone can remove the hard disk or steal the computer!
Some suggestions for preventing this are:
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