Usually Hacking refers to the act of breaking down into the system or an unauthorized access to a system or network. Hacking attacks are rising day by day, so that businesses are spending more on computer security. However, Hackers have developed new skills to break down a fully secured system. The "hacker" is a person who has strong computer and programming skills and extensive understanding of how the computer programs work. The art of hacking comes into scene in 1980s and soon became synonymous with illegal activity. In early 1980s, the Federal Bureau of Investigation (FBI) made its first arrest related to Hacking. A Milwaukee-based group known as the 414s was accused of breaking into 60 different computer systems including the Memorial Sloan-Kettering Cancer Center and the Los Alamos National Laboratory.

Hackers do not aim the same goal to break down into systems. One breaks the systems for just the purpose of damaging the system while other steals very sensitive information or data from the system, stealing money, collapse the networks. Some hackers break down the system for just the fun (As I do usually). There are many hacking attacks performed in the history by some famous attackers. In 2011, hackers gained access to Sony's PlayStation Network, putting at risk credit card data for more than 70 million people. The gaming service was closed for weeks and customers were eventually compensated with free games and subscriptions. Though the culprits were never caught, it is now believed that no data was stolen and the attack was intended to simply embarrass Sony. I will not list all of those attacks here. Jacob Appelbaum, Albert Gonzalez, Ed Cummings and Dan Kaminsky are some of the famous hackers. Ankit Fadia is a famous hacker from India, who has served government and many foreign institutes by his security knowledge and expertise.

Now coming to the classification of the hackers, they are categorized into 7 subgroups. "White Hat Hackers" breaks security for non-malicious reasons such as to test their own system or working for a company that produces the security software. "Black Hat Hackers" violates computer security for some cause beyond cruelty or for personal gain. They break down into networking system to destroy some data or make the system unusable for those who are authorized to access the system. A" grey hat hacker" is a combination of a Black Hat and a White Hat Hacker. A Grey Hat Hacker may surf the internet and hack into a computer system for the lone reason of notifying the administrator that their system has been hacked. "Elite Hackers" are the most skilled persons. "Script Kiddie" are non-skilled persons who use the pre-packaged security tools created by others like vulnerability scanners, IP address scanner, etc. "Neophyte" are the new to hacking and almost has no knowledge of how the technology and hacking works. "Blue Hat Hacker" is the person who works individually or for company to find the exploits and vulnerability before the launch of its product so that they can fix the exploit before releasing the product. A "Hacktivist" is a hacker who utilizes technology to announce a social, ideological, religious, or political message. In general, most hacktivism involves website defacement or denial-of-service attacks. "Nation states" are Intelligence agencies and cyberwarfare operatives of nation states. "Organized criminal gangs" performs criminal activity carried on for profit. For example, you might have been heard about the websites that offer hacking of e-mail and passwords for social networking sites such as Facebook. You have to pay their fees for hacking your victim. "Bots" are the automated software tools; some of them are freeware that are available for anykind of hacker. Cain and Abel, Net tools are some of the examples of bots.

There are many forms of hacking such as thieving passwords, stealing responsive data, breaking the software codes for serial numbers, etc. You need to seize the vulnerability of any software or website in order to perform attack. Viruses and worms are self-replicating programs or code fragments that attach themselves to other programs (viruses) or machines (worms). Both viruses and worms attempt to shut down networks by flooding them with massive amounts of bogus traffic, usually through e-mail. You can also program a virus or worm to hack into computer systems.

Trojan horses are the powerful programmed form of virus, which are attached to other programs, are leading cause of major break-ins. These types of Trojan horses are uploaded into internet servers for users. Once user downloads the Trojan horse which is attached with the other program, it gives total control over victim's PC to hacker. DoS attacks give hackers a way to bring down a network without gaining internal access. DoS attacks work by flooding the access routers with bogus traffic. Distributed DoSs (DDoS5) is coordinated DoS attacks from multiple sources. A DDoS is more difficult to block because it uses multiple, changing, source IP addresses.

Sniffing refers to the act of intercepting TCP packets. This interception can happen through simple eavesdropping or something more sinister. Spoofing is the act of sending an illegitimate packet with an expected acknowledgment (ACK), which a hacker can guess, predict, or obtain by snooping. Password cracking is the process of recovering passwords from data that has been stored in or transmitted by a computer system. A common approach is to repeatedly try guesses for the password.

Keyloggers are designed to record every key stroke on an affected machine for the purpose of latter retrieval. It gathers private information or passwords which a user enters by pressing the key. Modern keyloggers records mouse cursor also. They can be operated remotely and provide information about victim such as personal data.

Hackers typically use some social engineering tactics to get enough information to access the network. A common practice for hackers, who use this technique, is to contact the system administrator and play the role of a user who cannot get access to his or her system. Hackers who use this technique have to be quite savvy and choose the words they use carefully, in order to trick the system administrator into giving them information. In some cases only an employed help desk user will answer the phone and they are generally easy to trick.

Phishing is another popular option for hackers. They create a fake login page for particular website, hosts on any web host service for some time and creates a link for that fake web page. Website users are offered to click the link and they are being redirected to hacker's area and get him to enter victim's password. The password entered in the fake page is mailed to the hacker's mailbox. Cookie stealing works well for the hackers.

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