protection, similar to network access control and an encryption key. You could improve data encryption through rotation of the key. Think of this as having your own personal locksmith periodically show up at your home and change all the locks on your doors and windows. You dictate how often the key should be changed. Setting up a fence is another option, with the firewall as a correspondence. The firewall acts as a filter, letting authorized traffic in and locking other traffic out. One single way of protection is not enough, but there are protection concepts that are quite broad, with IPsec as the most well-known one. With this in mind it is obvious that the security plan in reality is distributed all over the network. Therefore, one way is to attach a security part to all other fundamental plans to ensure that they are all functioning properly. However, there would still be a need to have a chapter with no correspondence in the other plans, with the overall security policy and the translation from security language to concrete measures in the network. A common complementing or alternative way is to use layered protection. Both methods will be used. 6.6 MAIN WAYS TO IMPLEMENT SECURITY 6.6.1 SECURITY POLICY IN A COMPANY Security policies are in conflict with user friendliness. The tighter the security, the less is the convenience to users. Users will therefore find a way around a policy if it's too difficult to comply with. Some general security advice: Understand how your system normally functions. Notice unusual events that can help you to catch intruders before they damage the system. Use auditing tools to detect unusual events. You should know exactly which software you rely on, and your security system should not have to rely upon the assumptions that all software is bug-free or that your firewall can prevent all attacks. Create appropriate barriers inside your system SO that if intruders access one part of the system, they do not automatically have access to the rest of the system. The security of a system 