These can be classified into 3 groups

1. Unauthorized access or break-ins

• A system or network data is accessed by unauthorized personnel or system
• A hacker using a computerized server on a distribution site for private software’s or MP3s
• Occurs when unauthorized entry is gained to an asset / valuable thing such as computer and the unauthorized individual has the possibility of tampering asset.

2. Privacy violation or impersonation

• Access can be gained by a privacy violation or by exploiting a weakness in the security of a machine or hardware/software product.
• Once access to system is achieved data alternation or destruction can happen
• Viruses, worms and Trojans horses are some techniques that cause data alternation
• Privacy violations can happen via packet snooping or eavesdropping
• It can be accomplished using a packet sniffer on the LAN or anywhere on network where information is not encrypted
• Sniffer technology is available as software that can run on any laptop so if a hacker puts a PC on a LAN segment, they might be able to view all the packets on LAN
• To protect against privacy violations, physical security of network is an import step along with encryption and firewall.

3. Unavailable service or DDOS

• An attack that floods a network access so that user data or system cannot be accessed.
• Unavailable service occurs when authorized users cannot access a computer system due to an attacker’s attempt to disrupt access
• In DDOS (Distributed Denial of Service) attacks, acker send flood traffic or requests to computer systems and the system get so overwhelmed with these false requests, that they cannot respond to authorized user requests
• The type of traffic sent to cause problems has included ping ICMP, HTTP, DNS and SNMP.