The Nature Of Attacks

• To obtain unauthorised access to private, or secret, information stored on the compromised system -- recently the target has often been credit card numbers stored on commerce servers. Such access can be obtained by a wide variety of means. This is probably the most important type of attack.
   
  
• To use the compromised system as a start point for attacks on other, more interesting, systems whilst "covering their tracks" -- the (so-called) Springboard Attack.
   
  
• Denial of service (DOS) attacks attempt to use up system resources to inconvenience legitimate users. A classic example is to send vast megabytes of (anonymous) electronic mail to a target host in an attempt to exhaust its disk space. The (relatively) recently developed Distributed Denial of Service (DDOS) attacks are a particularly nasty form.
   
  
• A variation of the denial-of-service attack is where a Bad Guy actually attempts to cause damage to the compromised system, for example, by removing important files, changing configurations, etc. Recent "Web site defacements" come under this category.
   
  
• etc, etc...