Attacks can be divided into three main categories:

- Reconnaissance Attacks Hackers attempt to discover systems and gather information. In most cases, these attacks are used to gather information to set up an access or a Denial of Service (DoS) attack. A typical reconnaissance attack might consist of a hacker pinging Internet Protocol (IP) addresses to discover what is alive on a network.The hacker might then perform a port scan on the system to see which applications are running, and to try to determine the operating system (OS) and version on a target machine.

- Access Attacks An access attack is one in which an intruder attempts to gain unauthorized access to a system to retrieve information. Sometimes the attacker has to gain access to a system by cracking passwords or using an exploit. At other times, the attacker already has access to the system, but needs to escalate his or her privileges.

- DoS Attacks Hackers use DoS attacks to disable or corrupt access to networks, systems, or services.The intent is to deny authorized or valid users access to these resources. DoS attacks typically involve running a script or a tool, and the attacker does not require access to the target system, only the means to reach it. In a Distributed DoS (DDoS) attack, the source consists of many computers that are usually spread across a large geographic boundary.

Recognizing Network Security Threats

In order to effectively protect your network, you must consider the following question: From who or what are you protecting it? In this section, we approach the answer to that question from three perspectives:

- Who are the people that break into networks?

- Why do they do what they do?

- What are the types of network attacks and how do they work? First we look at intruder motivations and classify the various types of people who have the skill and desire to hack into others’ computers and networks.

Understanding Intruder Motivations

There are probably as many different specific motives as there are hackers, but the most common intruder motivations can be broken down into a few broad categories:

- Recreation Those who hack into networks “just for fun” or to prove

their technical prowess; often young people or “antiestablishment” types.

- Remuneration People who invade the network for personal gain, such as those who attempt to transfer funds to their own bank accounts or erase records of their debts, and “hackers for hire” who are paid by others to break into the network. Corporate espionage is also included in this category.

- Revenge Dissatisfied customers, disgruntled former employees, angry competitors, or people who have a personal grudge against someone in the organization. The scope of damage and the extent of the intrusion are often tied to the intruder’s motivation.

Recreational Hackers

Teen hackers who hack primarily for the thrill of accomplishment, often do little or no permanent damage, perhaps only leaving “I was here” messages to “stake their claims” and prove to their peers that they were able to penetrate your network’s security. There are also more malevolent versions of the fun-seeking hacker.These cybervandals get their kicks out of destroying as much of your data as possible or causing your systems to crash.

Profit-motivated Hackers

Hackers who break into your network for remuneration of some kind either directly or indirectly are more dangerous. Because money is at stake, they are more motivated than other hackers to accomplish their objective. Unfortunately, the number of these hackers is increasing dramatically, especially with the profitability of identity theft. Furthermore, because many of them are “professionals”, their hacking techniques could be more sophisticated than those of the average teenage recreational hacker. Monetary motivations include:

- Personal financial gain

- Corporate espionage

- Third-party payment for the information obtained

Those motivated by the last goal are almost always the most sophisticated, and the most dangerous. Money is often involved in the theft of identity information. Identity thieves can be employees who have been approached by any number of malicious organizations and offered money or merchandise or even threatened with blackmail or physical harm. In some instances, hackers go “undercover” and seek a job with a company in order to steal data that they can give to their own organizations.To add insult to injury, these “stealth spies” are then paid by your company at the same time they’re working against you. There are also “professional” freelance corporate spies that can be contracted to obtain company secrets, or they might do it on their own and auction the data off to competitors. These corporate espionage agents are often highly skilled.They are technically savvy and intelligent enough to avoid being caught or detected. Fields that are especially vulnerable to the threat of corporate espionage include:

- Oil and energy

- Engineering

- Computer technology

- Research medicine

- Law

Any company on the verge of a breakthrough that could result in large monetary rewards or worldwide recognition, should be aware of the possibility of espionage and take steps to guard against it.