"Computer security is at a crossroads. It's failing, regularly, and with increasingly serious results." [1] The weakest link in an organization may often be said to be the employees themselves (i.e., human behavior as a potential security threat), but not always! Even though the PC users within an organization are weak elements in any network security solution, organizations are also just as weak themselves. For instance, an organization might have network connections that are not configured (or properly configured), use network security tools that doesn’t support its purpose, or have created, implemented, and enforced their own security policy(ies) without consulting an expert; an organization setup like this is vulnerable to network threats and attacks.

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Network Security
Network security is important and is an essential element in maintaining any network. It involves safeguarding computing resources, ensuring data integrity, limiting access to authorized users, and maintaining data confidentiality. Designing a secure network requires incorporating fault-tolerant systems and solutions. One such solution is for an organization to use a network access control (NAC) to control access to networks.
Network Threats
Many computer-related threats spread by means of a network. When a network has been targeted or hit with a threat, it will likely infect other computers and PC users if not stopped.
Organizations need to be concerned about the security of their networks as there are many threats (e.g., viruses, malware, adware, spyware, Trojan horses, and others) that can infect a computer on a network. The most common threats for an organization nowadays have been malware and spyware. These are just a few of the common network security problems that occur within an organization.
If a network is not scanned (i.e., use a vulnerability scanner) or makes use of one of several network security tools (e.g., a network protocol analyzer, network intrusion detection and prevention system, a sniffer, port scanner, etc...) available (often for free) on the Web, it will likely be vulnerable to a network threat. Often, a Network Administrator or an IT Administer or manager will oversee the security of a network, but they might not always able to find all network threats; therefore, it's really every PC user's responsibility to check, scan and clear each disk, CD, DVD, and e-mail attachments that may carry malicious content onto a network (e.g., Internet, Intranet, Extranet).
Security Attacks
Security attacks are often used maliciously to consume and destroy the resources of a network. When attacks are sent (often times by a hacker, criminal, disgruntled or ex-employee) on a network, they use critical system resources (such as the CPU and RAM) to disrupt and damage an organizations' business operation, or to install some type of malicious program.
Note: Most network attacks fall into the category of Denial-of-Service (DoS): it's when an attacker attempts to prevent PC users from accessing information or services.
Since network intrusion attacks are a growing threat to organizations, systems managers should add an IDPS, an intrusion detection and prevention system, to their security infrastructure.