Unprotected computers are prone to computer viruses. Computer viruses are a computer program that can replicate itself and spread from one computer to another. This will affect or infects the computer negatively. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by other computer. Viruses may harm a computer system's data or performance. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious or simply do nothing to call attention to them. Some viruses do nothing beyond reproducing themselves. Sometimes we are confused about Trojan horses and worm, we think that they are the same but they are technically different. A worm can exploit security vulnerabilities to spread itself automatically to other computers through networks, while a Trojan horse is a program that appears harmless but hides malicious functions. A virus is really defined by its payload. Payload refers to a specific part of the virus, specifically, the part that is delivered to your computer. Just like a bomb delivers a payload of explosive material to a target, a virus delivers a payload of damaging code to your computer. A honey pot is a computer system on the Internet that is expressly set up to attract and trap people who attempt to penetrate other people's computer systems. A botnet is a collection of compromised computers connected to the Internet. When a computer is compromised by an attacker, there is often code within the malware that commands it to become part of a botnet. The "botmaster" or "bot herder" controls these compromised computers via standards based network protocols such as IRC and http.
Spoofing is the creation of TCP/IP packets using somebody else's IP address. Routers use the "destination IP" address in order to forward packets through the Internet, but ignore the "source IP" address. That address is only used by the destination machine when it responds back to the source. You can also spoof trough email,and this is called email spoofing. It is an activity in which the sender address and other parts of the email header are altered to appear as though the email originated from a different source. Denial of service attacks is an assault whose purpose is o distrust computer access to n Internet service. Perpetrators carry out Dos attack in a different ways. They may use unsuspecting computer to send many confusing data messages to a computer network, if the victim jams, it blocks legitimate visitors from accessing the network. A backdoor is a program or set of instructions in a program that allow users to bypass security controls when accessing a program, computer or network.A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass.
Sources:
Burger, Ralph, 1991. Computer Viruses and Data Protection
Shelly,Gary B.,2007. Discovering computers
