what is virus, trojan, worm and spyware?

every person who ever used a computer and or know about computers, must have heard the word computer virus that could attack the computer. Computer viruses sometimes upsetting computer users. Often we hear the word computer viruses, but rarely know what the definition of computer virus itself. But in addition to computer viruses, there is also the type of a program that can damage a computer system, such as trojans, worms, spyware and others. Here are some explanations:

• A computer virus is a computer program that duplicate or replicate by inserting copies of itself into the storage media / documents and into the network secretly without the knowledge of computer users. The effects of computer viruses are very diverse ranging from only appear strange messages to damage the computer and delete files or documents we. 
• Worm is a potential security weaknesses or gaps in our computers that allows the computer is infected with the virus without having to execute a file that generally occur on the network.
• Trojan is a program that allows our computer controlled others through the network or the Internet. 
• Spyware is an application that leaked the information data or user behavior habits in using the computer to an outside party without us knowing it. Usually used by the party advertisers.

If we see irregularities in the storage medium such as a file called strange that we never made or file is not the type of applications but admitted as an application then do not we click, we go or we run for a computer virus is not transmitted to the computer that we use.Computer Signs You Exposed / Infected destroyer program computer system: 

1. The computer is running slower than normal 
2. Often out corrupted messages
3. Change the display on a computer
4. Storage media such as floppy disks, flash, and so directly copy the files strange without our coffee when we connect to the computer.
5. Computer crash like to restart itself or while walking.
6. Like the message or writing strange
7. The computer stopped working
8. Hard Drive not accessible
9. Printer and other devices can not be used even though no hardware problems and software drivers.
10. Often there is a menu or dialog box that an error or broken.
11. Loss of some basic computer functions.
12. The computer attempts to connect themselves with the Internet or a network without our order. 
13. Files that we store on computers or storage media go away or hidden viruses. and others ...

• Sample forms of media dissemination of computer viruses from one computer to another computer:Storage Media (diskettes, flash, external hard drive, zipdisk, cd, dvd, bluray disc, cartridge, etc.) 
• The network lan, wan, man, internet and so forth.
• File attachment or file attachments in emails or other electronic messages. 
• File software (software) virus-ridden computer.