Computer Virus is a program / application that can replicate itself and spread by inserting itself in other programs and data. usually the user does not know if the computer in his possession terjangkit virus until one of the data is lost or the existing programs on the computer can not run.
Computer viruses are generally created for bad purposes, many negative effects are caused by computer viruses such as reproduce itself so that memory becomes small, this makes the computer often hang or freeze, then change the extension on the files and programs that make the program / file it can not be used, and can also steal personal data someone without the person's knowledge. besides that virus can also damage hardware on computer.
In fact almost 95% of viruses attack users of windows operating system. The rest attacked Linux / GNU, Mac, FreeBSD, OS / 2 IBM, and Sun Operating System.
The types of viruses on the computer
Worm - Duplicate itself on the hard drive. This makes the computer resources (Harddisk) to be full of the worm.
Trojan - Takes data on the infected computer and sends it to the trojan maker itself.
Backdoor - Almost the same as trojan. However, Backdoor usually resembles files that are fine. For example games.
Spyware - A virus that monitors an infected computer.
Rogue - a program that mimics an antivirus program and displays activity like a normal antivirus, and gives fake alerts about viruses. The goal is for users to purchase and activate the fake antivirus program and bring money to the creator of the rogue virus. Also rogue can open a security hole in the computer to bring in other viruses. Rootkit - The working virus resembles the work of an ordinary computer system.
Polymorphic virus - A fickle virus that can not be detected.
Metamorphic virus - A virus that modifies its own coding to make it more difficult to detect.
Mobile virus - A virus that runs on cell phones, and can cause a variety of effects, ranging from damaging cell phones, stealing data in the cell phone, to making calls silently and spend the pulse of mobile phone users.