A hacker is a person who breaks into a computer system. The reasons for hacking can be many: installing malware, stealing or destroying data, disrupting service, and more. Hacking can also be done for ethical reasons, such as trying to find software vulnerabilities so they can be fixed.
Hackers breach defenses to gain unauthorized access into computers, phones, tablets, IoT devices, networks, or entire computing systems. Hackers also take advantage of weaknesses in network security to gain access. The weaknesses can be technical or social in nature.
Much of today's computer hacking has been automated--which is why it currently poses such a threat to Internet security. Some hackers are still highly trained technical professionals, but others are much less skilled and are able to launch successful attacks simply by buying attack tools.
Hacking today takes on so many forms and targets so many kinds of organizations that a multilayered defense strategy is necessary for every company and government agency. This strategy must address people, processes, and technology.
Ethical hacking involves the legal use of hacking techniques for benevolent versus malicious purposes. Ethical hackers use penetration testing and other tactics to find software vulnerabilities and other security weaknesses so they can be promptly addressed.
Cybercriminals are hackers who often use tools such as malware, phishing, and ransomware to launch attacks for financial gain or other nefarious purposes. They steal information ranging from email addresses and passwords to social security numbers and credit card details in order to sell it for profit.
Hacktivists use hacking techniques as a tool for social activism. They often break into organizations they oppose in order to send a message, for instance by defacing their website, launching DDoS attacks, stealing and posting personal or confidential information, and so on. Anonymous is one example of a well-known hacktivist group.
Ethical hackers are legally permitted to break into certain computer systems to find flaws. Businesses and government organizations often hire ethical hackers to uncover software vulnerabilities or other security weaknesses so they can be fixed before they are exploited by malicious hackers.
Script kiddies are part of the newer wave of hackers who do not rely on high levels of skill for their attacks. Instead they purchase and use ready-made scripts and hacking tools.