Computer Virus | Types of Virus | History of Computer Virus

We all must have heard of the term virus, even many of you have also had an attack of viruses on our body or might have suffered from viral fever, which may have left you weak. Unlike bioligical viruses attack our body system, computer viruses attack a computer system.

What is Computer Virus?

A computer virus is a kind of malicious computer program that enters the computer system by attaching itself to another computer program, and replicates itself across the system. When the replication is succeeds, this code infect the other files and program present on your system.

In more technical terms, a computer virus is a type of malicious code or program written. The term virus stands for "Vital Information Recourse Under Siege". Viruses spread from one computer to another or other sources. It becomes active when you start an infected application or start you computer from a disk whith infected system files. Once the viruses in the computer's memory it usually infects any application to run. Different viruses behave in different ways. Some stay active in the memory until the computer is shut down or other may remain active only as long as the infected application is running.

What are the sign of a Computer Virus?

A computer virus attack can produce a variety of symptoms. Here are some of them:

Frequent pop-up windows : Pop-ups might encourage you to visit unusual sties. Or they might prod you to download antivirus or other software programs.
Changes to your homepage : Your usual homepage may change to another website, for instance. Plus , you may be unable to reset it.
Mass emails being sent from your email account : A criminal may take control your account or sends emails in your name from another infected computer.
Frequent crashes : A virus can inflict major damage on your hard drive. This may cause your device to freeze or crash. It may also prevent your device from comming back on.
Unusually slow computer performance : A sudden change of processing speed could signal that your computer has a virus.
Unknown program that start up when you turn on your system : You may become aware of the unfamiliar program when you start your computer. Or you might notice it by checking your computer's list of active application.
Unusual activities like password changes : This could prevent you from logging into your computer

What are the different types of Computer Viruses?

1. Boot sector virus

This types of virus infects the boot sector of floppy disk or the Master Boot Record(MBR) of hard disks. It can take control when you start or boot your computer. One way it can spread is by plugging an infected USB drive into your computer.

2. Web Scripting Virus

This type of virus exploits the code of web browsers and web pages. If you access susch a web page , the virus can infect your computer.

3. Browser Hijacker

A virus that can change the setting on your browser will hijack browser favorites, the home page URL, your search preferences and redirect you to a malicious site. The site could be a phishing site or an adware page used to steal data or make money for attacker.

4. Resident Virus

A virus which saves itself in the memory of the computer and the infects other files and programs when its originating program is no longer working. This virus can easily infect other files because it is hidden in the memory and is hard to be removed from the system.

5. Direct Action Virus

When a user executes a seemingly harmless file attached with malicious code, direct action viruses deliver a payload immediately. These viruses can also remain dormant until a specific action is taken or a timeframe passes.

6. Polymorphic Virus

Malware authors can use Polymorphic code to change the program's footprint to avoid detection Polymorphic viruses make it more difficult for an antivirus to detect and remove them.

7. File Infect Virus

As the name suggests, it first infects a single file and then later spreads itself to other executable files and programs. The main source of this virus are games and word processors.

8. Multipartite Virus

These malicious programs spread across a network or other systems by copying themselves or injecting code into critical computer resources.

9. Macro Virus

Microsoft Office files can run macros, and these macros can be used to download additional Malware or run malicious code. Macro viruses deliver a payload when the file is opened, and the macro runs.

How to Protect Your Computer?

Computer Viruses can damage your PC, send sensitive data to attackers, and cause downtime until the system is repaired. You can avoid becoming the next computer virus victim by following a few best practices:

Install antivirus software : Antivirus should run on any device connected to the network. It's your first defense against viruses. Antiviruses software stops malware executables from running on your local device.
Don't Open executable email attachments : Many malware attacks including ransomware start with a malicious email attachment. Executable attachment should never be opened, and users should avoid running macros programmed into files such as Microsoft Word or Excel.
Keep Your Operating System Updated : Developers for all major operating systems release patches to remediate common bugs and security vulnerabilities, Always keep your operating system updated and stop using end-of-life version (Windows 7 or windows 10).
Avoid Questionable Websites : Older browsers are vulnerable to exploits used when just browsing a website. You should always keep your browser updated with the latest patches, but avoiding these sites will stop drive-by downloads or redirecting you to sites that host malware.
Don't use Pirated software : Free pirated software might be tempting, but it's often packaged with malware. Download vendor software only from the official source and avoid using software that's pirated and shared.

What is a Computer Worm?

A computer worm is malware, just like a virus, but a worm takes a copy of itself and propagates it to other users. Worms can also deliver a payload and exhaust resources. For example, an Email worm sends a copy of itself to everyone on an infected user's email contact list. When it reaches recipient inboxes, anyone who runs the worm sends it to their contact list. Email worms exhaust storage space and spread very quickly across the internet, so they create issues differently than a virus.

Examples of Computer Virus

The web contains millions of computer viruses, but only a few have gained popularity and infect record numbers of machines. Some examples of widespread computer viruses include:

Morris Worm
Nimda
ILOVEYOU
SQL Slaimmer
Stuxnet
CryptoLocker
Cronficker
Tinba
Welchia
Shlayer