The
layered approach was developed to accommodate changes in the evolving technology. Each OSI layer is
responsible for a specific function within the networking stack, with information flowing up and down to
the next subsequent layer as data is processed. Unfortunately, this means that if one layer is hacked,
communications are compromised without the other layers being aware of the problem. For example, as
shown in Figure 1-5, if the physical layer (Layer 1) was compromised, it could cause all other layers to be
compromised in succession. Security is only as strong as the weakest link. When it comes to networking,
any layer can be the weakest link.
Figure 1-5. The Domino Effect
Security Wheel
Network security is a continuous process built around the corporate security policy. The security wheel depicted
in Figure 1-6 shows a recursive, ongoing process of striving toward perfection??”to achieve a secured network
infrastructure. The paradigm incorporates the following five steps:
Step 1. Develop a security policy
A strong security policy should be clearly defined, implemented, and documented, yet simple
enough that users can easily conduct business within its parameters.
Step 2.
Pages:
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66