title: Security appliance
text: # Security appliance
  
  A security appliance is any form of server appliance that is designed to protect computer networks from unwanted traffic.
  
  ## Types of security appliances
  
  * Active devices block unwanted traffic. Examples of such devices are firewalls, anti virus scanning devices, and content filtering devices.
  * Passive devices detect and report on unwanted traffic, such as intrusion detection appliances.
  * Preventative devices scan networks and identify potential security problems (such as penetration testing and vulnerability assessment appliances).
  * Unified Threat Management (UTM) appliances combine features together into one system, such as some firewalls, content filtering, web caching etc.
  