Human Threats
Malicious threats consist of inside attacks by disgruntled or malicious employees and outside attacks by non-employees just looking to harm and disrupt an organization.
The most dangerous attackers are usually insiders (or former insiders), because they know many of the codes and security measures that are already in place. Insiders are likely to have specific goals and objectives, and have legitimate access to the system. Employees are the people most familiar with the organization's computers and applications, and they are most likely to know what actions might cause the most damage. Insiders can plant viruses, Trojan horses, or worms, and they can browse through the file system.
The insider attack can affect all components of computer security. By browsing through a system, confidential information could be revealed. Trojan horses are a threat to both the integrity and confidentiality of information in the system. Insider attacks can affect availability by overloading the system's processing or storage capacity, or by causing the system to crash.
People often refer to these individuals as "crackers" or "hackers." The definition of "hacker" has changed over the years. A hacker was once thought of as any individual who enjoyed getting the most out of the system he or she was using. A hacker would use a system extensively and study it until he or she became proficient in all its nuances. This individual was respected as a source of information for local computer users, someone referred to as a "guru" or "wizard."