Chapter 7 Firewall for FortiOS 5.0 : Network defense
  
Network defense
This section describes in general terms the means by which attackers can attempt to compromise your network and steps you can take to protect it. The goal of an attack can be as complex as gaining access to your network and the privileged information it contains, or as simple as preventing customers from accessing your web server. Even allowing a virus onto your network can cause damage, so you need to protect against viruses and malware even if they are not specifically targeted at your network.
The following topics are included in this section:
Monitoring
Blocking external probes
Defending against DoS attacks