Computer crimes are basically one of the criminal activities in which the computer or network is a necessary part of the crime, these terms are also sometimes used to include traditional crimes, such as fraud, theft, blackmail, forgery, and hacking in which computers or networks are used to facilitate the illicit activity. Below are some of the description of the crimes.

COMPUTER FRAUD
Computer fraud is the act of using a computer to commit fraud. Computer fraud is a criminal offense punishable by jail time and fines under the Computer Fraud and Abuse Act. Impacts cause by the computer fraud had affected the financial of company’s business in great losses and even cause business to be close down. Criminals tend to use computer to access the company’s account without proper authorization. For example, there is a case whereby a former accounts payable clerk, Jessica Quitugua Sabatia, using her computer to access North Bay’s accounting software without authorization, and in turn issued approximately 127 checks payable to herself and others. Several of the checks were cashed by Sabatia or deposited into her personal bank account, and some were deposited into the bank accounts of others. These had resulted in losses to North Bay of at least $875,035.


HACKING

Hacking is one type of computer crimes. In a security context, a Hacker is someone involved in computer security/insecurity, specializing in the discovery of exploits in systems (for exploitation or prevention), or in obtaining or preventing unauthorized access to systems through skills, tactics and detailed knowledge.

Common Methods

Here are some of the common methods which hackers normally use and the impact of these attack:

• Security exploit

A security exploit is a prepared application that takes advantage of a known weakness.

• Vulnerability scanner

A vulnerability scanner is a tool used to quickly check computers on a network for known weaknesses. Hackers also commonly use port scanners. These check to see which ports on a specified computer are "open" or available to access the computer, and sometimes will detect what program or service is listening on that port, and it's version number. (Note that firewalls defend computers from intruders by limiting access to ports/machines both inbound and outbound, but can still be circumvented.)

• Packet Sniffer

A packet sniffer is an application that captures TCP/IP data packets, which can maliciously be used to capture passwords and other data while it is in transit either within the computer or over the network.

• Spoofing attack

A spoofing attack is a situation in which one person or program successfully masquerades as another by falsifying data and thereby gaining illegitimate access.

• Social engineering

Social engineering means convincing other people to provide some form of information about a system, often under false premises. A blatant example would be asking someone for their password or account possibly over a beer or by posing as someone else. A more subtle example would be asking for promotional material or technical references about a company's systems, possibly posing as a journalist.

• Trojan horse

A Trojan horse is a program designed as to seem to being or be doing one thing, such as a legitimate software, but actually being or doing another. They are not necessarily malicious programs. A trojan horse can be used to set up a back door in a computer system so that the intruder can return later and gain access. Viruses that fool a user into downloading and/or executing them by pretending to be useful applications are also sometimes called trojan horses. (The name refers to the horse from the Trojan War, with conceptually similar function of deceiving defenders into bringing an intruder inside.)

• Virus

A virus is a self-replicating program that spreads by inserting copies of itself into other executable code or documents. Thus, a computer virus behaves in a way similar to a biological virus, which spreads by inserting itself into living cells.

• Worm

Like a virus, a worm is also a self-replicating program. The difference between a virus and a worm is that a worm does not create multiple copies of itself on one system: it propagates through computer networks. After the comparison between computer viruses and biological viruses, the obvious comparison here is to a bacterium. Many people conflate the terms "virus" and "worm", using them both to describe any self-propagating program. It is possible for a program to have the blunt characteristics of both a worm and a virus.

http://en.wikipedia.org/wiki/Hacker_%28computer_security%29

Impact of hacking on business
From the above methods, there are three different types of goals that will be affected as a result of the hacking. They are “confidentiality”, “integrity” and “availability”. For confidentiality, it means that information which cannot be review to the public is being exposing to external parties. For example, client’s credit card number is being posted in a forum. For integrity, there is no trust on the information. The information has been changed and it is no longer accurate. For example, a company’s database had been edited by an unknown user. For availability, it means that company resources cannot be access. For example, user is unable to access to an e-business company’s website and causes lost of profit.

Denial of Service (DOS)
A denial of service (DOS) attack is an incident in which a user or organization is deprived of the services of a resource they would normally expect to have. Typically, the loss of service is the inability of a particular network service, such as e-mail, to be available or the temporary loss of all network connectivity and services.

This type of attack does not involve breaking into the target system. Usually a successful DoS attack reduces the quality of the service delivered by some measurable degree, often to the point where the target infrastructure of the DoS attack cannot deliver a service at all.

A DoS attack attempts to reduce the ability of a site to service clients, be they physical users or logical entities such as other computer systems. This can be achieved by either overloading the ability of the target network or server to handle incoming traffic or by sending network packets that cause target systems and networks to behave unpredictably.

In conclusion, the fundamental issue in most computer crime is the criminals' lack of respect for the property or privacy of other people. Hence, hope that society will recognize the seriousness of computer crime and demand more severe punishment for such criminals.