A computer virus is a malicious software program loaded onto a user’s computer without the user’s knowledge and performs malicious actions. Viruses can enter your computer as attachments to an email or in a downloaded file, or they can be hidden on a zip drive. It's usually not obvious that a virus is present.
Even if you’re careful, you can pick up computer viruses through normal Web activities like:
- Sharing music, files, or photos with other users
- Visiting an infected website
- Opening spam email or an email attachment
- Downloading free games, toolbars, media players and other system utilities
- Installing the fake mainstream software applications
Imagine typing in an internet address and automatically bouncing through several different sites. When this happens, a browser hijacker is responsible for the incident. Unfortunately, hijackers are usually attached to appealing toolbars, programs and other free downloads you choose. They often have the word "search" in their names. A good security program can detect nearly all of these.
This form of computer virus is very destructive. It embeds itself in the computer's memory to carry out operations. This means whenever you run your operating system, the virus is working. It has varying effects, but it will clear up space on your computer for its own use by corrupting and deleting your files.
File Infector Virus
This virus also infects executable files or programs. When you run these programs, the file infector virus is activated as well which can slow down the program and produce other damaging effects. A large block of existing viruses belongs to this category.
These viruses are harder to detect. This is because security programs scan coding to identify viruses, but these specific viruses both encrypt and change their coding. They continually changing their operations over time, which may affect the programs you use.
Basically, this type of virus spreads out through Local Network Area (LAN) and through the internet. These viruses replicate through shared resources, including drives and folders. When network viruses enter a computer, they look for their potential prey. Dangerous network viruses include Nimda and SQLSlammer.
A virus is a malicious computer program designed to harm
your PC. There are different types which can corrupt the whole system or delete
all your files. They are usually inserted into your computer via a harmless
document or program. That is why it is important to use a good anti-virus. Have
a look at this link: https://www.voipshield.com/20-common-types-of-viruses-affecting-your-computer/ . I am sure it will help you.
As in humans infective agents undermine immune system similar in nature but destroys data etc. causes computer to crash.