Any computer that is either physically accessible or can remotely be contacted over a network is potentially threatened by attempts to circumvent its security measures. The PC architecture is especially insecure and using a BOOT-Prom can help preventing some of the more obvious attacks. On the other hand, it also enables some attacks that are not possible against machines that boot from local mass storage devices (floppy, harddisk, ...). As a general rule, you can assume that it is impossible to protect your system from all conceivable attacks, but you can try to minimize the chance of an attack, try to minimize the seriousness of the damage caused and try to help in detecting attacks at the earliest possible moment. This text discusses some of the issues involved and tries to raise awareness of security problems; it cannot provide generic solutions to all of these problems, but should help you in appreciating the need for proper administration and regular security updates.