Whether wired or wireless, computer networks are essential to everyday activities. Individuals and organizations alike depend on their computers and networks. Intrusion by an unauthorized person can result in costly network outages and loss of work. Attacks to a network can be devastating and can result in a loss of time and money due to damage or theft of important information or assets.

Intruders can gain access to a network through software vulnerabilities, hardware attacks or through guessing someone's username and password. Intruders who gain access by modifying software or exploiting software vulnerabilities are often called hackers.

After the hacker gains access to the network, four types of threats may arise:

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Even in small networks, it is necessary to consider security threats and vulnerabilities when planning a network implementation.