Computer Viruses are unwanted software programs or pieces of code that interfere with the functioning of the computer.
They spread through contaminated files, data and insecure networks. Once it enters your system, it can replicate to produce copies of itself to spread from one program to another program and from one infected computer to another computer.
It is the simplest computer virus that overwrites the code of the host computer system's file with its own malicious code.
This virus appends its malicious code to the end of the host program's file.
Micro virus alters or infects the macros of a document or data file.
BootVirus or boot sector virus alters the boot sector program stored in the hard disk or any other storage device such as floppy disks.
The resident virus stays permanently in the primary memory (RAM) of the computer. When you start the computer, it becomes active and corrupts the files and programs running on the computer.
The non-resident virus does not reside in the memory of a computer. So it is not executed from the computer's' memory. For example executable viruses.
It mainly infects the executable files, the files with .com or .exe extensions.
Computer worm is similar to a virus but is technically different from the virus. It can replicate and spread like a virus, but unlike viruses, it does not need a host program to spread.
Trojan Horse is a malware like a virus or a worm, but it is technically different from both. It can't replicate like virus and worm.
It is also as a spacefilter virus. As the name suggests, the virus tends to install itself by occupying the empty sections of a file.
It infects the CMOS, Which stands for complementary metal-oxide semiconductor and is a memory chip that contains the system configuration. The virus can erase or reset the system configuration.
It resides itself in a file whose name is similar to another program file, which is executed normally. When the program file is executed, the virus gets activated and performs malicious steps such as deleting the files on your computer hard drive.
It encrypts its playload to make its detection more difficult. It compare two parts an encrypted virus body and a decryptor, which decrypts the virus when it is executed.
It is non-resident computer virus which resides in an executable file. Whenever the infected file is executed it infects the otehr files.
It creates its thousands of copies itself. In each copy, it changes the sequence and byte values to evade detection by antivirus software.
It is hidden computer virus, which specifically attacks operating system processes.
The machine may work slowly. e.g, it will take more time to open or shut down the computer while opening a file, document, computer application. The operating system and internet speed may get slow.
A virus may cause unusual frequent pop-ups on your window.
The hard drive may exihibit unusual high activity even when it is not in use. It may cause unwanted changes to your hard drive and may freeze or crash this device.
One may experience frequent sudden system crashes while playing games, watching videos, or doing some other work using the infected system. A blue screen appears when it crashes.
Unwanted programs may open or start automatically when you start your computer.
Your machine may perform differently, such as you may not be able to log into your accounts.
Sometimes, you experience high network activity even if you are not connected to the internet and vice versa.
We often see advertisements while browsing, but if you see them even when you are not browsing, it may indicate a virus on your computer.
You may experimence different colors in your display if your computer is affected by a virus.
Some viruses are developed to affect specific applications. Consequently, some applications may not work on your computer if it is infected.
A printer attached to an infected computer may print documents without getting any command or in an inappropriate manner.
One may see strange message on a computer screen such as error messages.
e.g- cannot rename folder.