“This series of articles will guide a fledgling Linux system
admin through entry level computer security routines. It will
consist of basic tutorials on subjects such as where to find Linux
security information, what services are vulnerable or have been
vulnerable in the past, encryption, firewalls, network intrusion
detection systems, and more.”
“In this first article, I will outline threats to which a
sysadmin should immediately respond. The three basic areas of
vulnerability are physical access, local area network access, and
remote access.”
“Physical access attacks are essentially impossible to defeat
strictly using software. If an attacker can physically access your
machine, your system can be compromised. For instance, physical
attacks may consist of using a simple root boot disk, or even just
yanking the hard drive. Physical security depends more on the
security of the entire building and the room where the system is
located.”