Internet security is a branch of computer security. It encompasses the Internet, browser security, web site security, and network security as it applies to other applications or operating systems as a whole. Its objective is to establish rules and measures to use against attacks over the Internet. The Internet is an inherently insecure channel for information exchange, with high risk of intrusion or fraud, such as phishing, online viruses, trojans, ransomware and worms. Many methods are used to combat these threats, including encryption and ground-up engineering. Threats Malicious software Malicious software comes in many forms, such as viruses, Trojan horses, spyware, and worms. Malware, a portmanteau of malicious software, is any software used to disrupt computer operation, gather sensitive information, or gain access to private computer systems. Malware is defined by its malicious intent, acting against the requirements of the computer user, and does not include software that unintentionally causes harm due to some deficiency. The term badware applies to both malware and unintentionally harmful software. A botnet is a network of computers that have been taken over by a robot or bot that performs large-scale malicious acts for its creator. Computer viruses are programs that can replicate their structures or effects by infecting other files or structures on a computer. The typical purpose of a virus is to take over a computer to steal data. Computer worms are programs that can replicate themselves throughout a computer network. Ransomware is a type of malware that restricts access to the computer system that it infects, and demands a ransom in order for the restriction to be removed. Scareware is a program of usually limited or no benefit, containing malicious payloads, that is sold via unethical marketing practices. The selling approach uses social engineering to cause shock, anxiety, or the perception of a threat, generally directed at an unsuspecting user. Spyware refers to programs that surreptitiously monitor activity on a computer system and report that information to others without the user's consent. One particular kind of spyware is key logging malware. Often referred to as keylogging or keyboard capturing, is the action of recording (logging) the keys struck on a keyboard. A Trojan horse, commonly known as a Trojan, is a general term for malware that pretends to be harmless, so that a user will be convinced to download it onto the computer. Denial-of-service attacks A denial-of-service attack (DoS) or distributed denial-of-service