Malware or malicious software is a program or code file that is dangerous and unsafe for a user computer. This code is specially designed to harm, interrupt, steal, delete, monitor or other illegal action on user computer or networks without any permission. The malware includes viruses, Trojan horse, worms, and spyware.
The virus is a kind of malware that spread out inserting a copy of itself into the user computer and fitting itself as a part of another program. It spreads from computer to computer. It reproduces and spread itself using programming files or document. A virus inserting or attaching itself to a valid program or document that supports macros to execute its code.
A virus has the power to cause harmful or destructive effects, for example, harming the system software by corrupting or destroying data which causing denial-of-service (DoS) conditions. All types of viruses are attached to an executable file, that will not be active until a user runs this affected file. When a user opens the affected file, a viral code is executed also. Usually, the affected program work but; viruses overwrite other programs with copies of themselves, which destroys the computer programs completely. Viruses also spread when the software or document are copied or transferred from one computer to another.
Computer worms are a type of malicious software just like viruses. It is a self-replicating program that duplicates functional copies of themselves and can cause the same type of damage like a virus. In comparing to viruses, which require infected host file to spread; worms are individual software and it does not require a host file, program or human help to spread.
The computer worms are not requiring attachment to a program to infect a host and enter a computer through vulnerability. The computer worms often use parts of a computer operating system that are automatic and invisible to the user. It is usually, noticed when it consumes maximum system resources, slowing and halting the computer tasks.
Trojan horse is another harmful program for computers. The cyber-thieves used Trojan to gain access to the user’s system. Users are usually tricked into loading and executing it on their systems by using some social engineering. Once it is executed on the user’s computer; it can steal users important data, it can also get backdoor access to the user’s system. Trojan horse can delete user data from the system. It is also used to activate and spread another malware program on the user’s computer.
Like viruses and worms, Trojan horses do not use the self-replicate method to infect other files. It should spread through user interaction such download files from the internet; accepting files while chatting to unknown persons and opening an e-mail attachment from an untrusted source.