What are computer viruses and how do they work?

A computer virus is a type of malware that, when executed, replicates itself by modifying other computer programs and injecting its own code. When this replication succeeds, the affected areas are then said to be “infected” with a virus. Virus writers use social engineering deceptions and exploit detailed knowledge of security vulnerabilities to initially infect systems and spread the virus. As a result, anti-virus software is becoming increasingly complex in order to overcome increasingly sophisticated viruses.

Computer viruses generally require some interaction with a user in order to propagate, such as opening an email attachment or executing a file from a removable drive. Unlike worms, computer viruses cannot propagate without some assistance from a user.

Once a system is infected with a virus, the virus can do any number of things. The most common is to simply replicate itself and infect other files on the system. This can quickly lead to a situation where the entire system is filled with copies of the virus, making it unusable. Other viruses might delete files on the system, encrypt files in an effort to hold the user’s data hostage (ransomware), or even display messages on the screen.

There are a number of ways that computer viruses spread. The most common is by email, where an infected attachment is sent to a large number of people in the hope that someone will open it. Once opened, the virus will replicate itself and spread to other files on the system. Another common method is to include the virus in a file that is shared on peer-to-peer networks. When someone downloads and opens the file, the virus will replicate and spread.

Computer viruses can cause a lot of damage to a system. They can delete files, encrypt data, and even render a system unusable. That’s why it’s important to have a good anti-virus program installed on your computer and to be careful about the files you open.

What are some of the most common computer viruses?

A virus is a code which has potential to copy itself and corrupt system. It spreads from one computer to another, leaving infections as it travels. It gets transmitted via removable media, downloads, and email attachments. It works by inserting itself to systems and applications, and when these are opened, the virus runs its malicious code. The most common types of computer viruses are:

1. Boot virus: It infects the computer’s boot sector which stores information about how the computer starts up. This type of virus is relatively rare nowadays.

2. File infector virus: As its name suggests, this virus infects files on your computer, usually executable files with .exe or .com extensions. The virus puts its own code into the file, which is run when the file is executed.

3. Macro virus: This virus is written in a macro language, which is built into many applications, such as Microsoft Word or Excel. When the infected document is opened, the virus runs its code, which can infect other documents on the same computer.

4. Multipartite virus: This virus can infect both files and the boot sector. It is one of the most difficult viruses to remove.

5. Polymorphic virus: This virus encrypts itself in a different way each time it infects a file, making it harder to detect and remove.

6. Rootkit: A rootkit is a type of virus which gives an attacker control over a computer without the owner’s knowledge. Once a rootkit is installed, it’s very hard to find and remove.

7. Spyware: Spyware is a type of virus which gathers information about a user without their knowledge. It can track what websites are visited, what keystrokes are made, and can even take control of the webcam.

8. Trojans: A Trojan is a type of virus which seems to be benign but is actually malicious. Trojans can delete files, steal information, or even give an attacker control over the computer.

9. Ransomware: Ransomware is a type of virus which encrypts files on the computer and demands a ransom be paid to decrypt them. It is one of the most serious types of virus, as it can render important files completely inaccessible.

10. Worms: Worms are similar to viruses, but they don’t need to attach themselves to files to spread. Instead, they can spread themselves through networks, infecting computers which are connected to the same network.

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