what is computer virus ?
A computer virus, much like a flu virus, is designed to spread from host to host and has the ability to replicate itself. Similarly, in the same way that flu viruses cannot reproduce without a host cell, computer viruses cannot reproduce and spread without programming such as a file or document.
In more technical terms, a computer virus is a type of malicious code
or program written to alter the way a computer operates and is designed
to spread from one computer to another. A virus operates by inserting
or attaching itself to a legitimate program or document that supports
macros in order to execute its code. In the process, a virus has the
potential to cause unexpected or damaging effects, such as harming the
system software by corrupting or destroying data.
How does a computer virus attack?
Once a virus has successfully attached to a program, file, or document, the virus will lie dormant until circumstances cause the computer or device to execute its code. In order for a virus to infect your computer, you have to run the infected program, which in turn causes the virus code to be executed.
This means that a virus can remain dormant on your computer, without showing major signs or symptoms. However, once the virus infects your computer, the virus can infect other computers on the same network. Stealing passwords or data, logging keystrokes, corrupting files, spamming your email contacts, and even taking over your machine are just some of the devastating and irritating things a virus can do.
While some viruses can be playful in intent and effect, others can
have profound and damaging effects. This includes erasing data or
causing permanent damage to your hard disk. Worse yet, some viruses are
designed with financial gains in mind.
How do computer viruses spread?
In a constantly connected world, you can contract a computer virus in many ways, some more obvious than others. Viruses can be spread through email and text message attachments, Internet file downloads, and social media scam links. Your mobile devices and smartphones can become infected with mobile viruses through shady app downloads. Viruses can hide disguised as attachments of socially shareable content such as funny images, greeting cards, or audio and video files.
To avoid contact with a virus, it’s important to exercise caution when surfing the web, downloading files, and opening links or attachments. To help stay safe, never download text or email attachments that you’re not expecting, or files from websites you don’t trust.
What are the signs 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 sites. 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 of your account or send 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 coming back on.
- Unusually slow computer performance. A sudden change of processing speed could signal that your computer has a virus.
- Unknown programs that start up when you turn on your computer. 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 applications.
- Unusual activities like password changes. This could prevent you from logging into your computer.
How to help protect against computer viruses?
- Use a trusted antivirus product, such as Norton AntiVirus Basic, and keep it updated with the latest virus definitions. Norton Security Premium offers additional protection for even more devices, plus backup.
- Avoid clicking on any pop-up advertisements.
- Always scan your email attachments before opening them.
- Always scan the files that you download using file sharing programs.
What are the different types of computer viruses?
1. Boot sector virus
This type of virus 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 such a web page, the virus can infect your computer.
3. Browser hijacker
This type of virus “hijacks” certain web browser functions, and you may be automatically directed to an unintended website.
4. Resident virus
This is a general term for any virus that inserts itself in a computer system’s memory. A resident virus can execute anytime when an operating system loads.
5. Direct action virus
This type of virus comes into action when you execute a file containing a virus. Otherwise, it remains dormant.
6. Polymorphic virus
A polymorphic virus changes its code each time an infected file is executed. It does this to evade antivirus programs.
7. File infector virus
This common virus inserts malicious code into executable files — files used to perform certain functions or operations on a system.
8. Multipartite virus
This kind of virus infects and spreads in multiple ways. It can infect both program files and system sectors.
9. Macro virus
Macro viruses are written in the same macro language used for
software applications. Such viruses spread when you open an infected
document, often through email attachments.
How to remove computer viruses
You can take two approaches to removing a computer virus. One is the manual do-it-yourself approach. The other is by enlisting the help of a reputable antivirus program.
Want to do it yourself? There can be a lot of variables when it comes to removing a computer virus. This process usually begins by doing a web search. You may be asked to perform a long list of steps. You’ll need time and probably some expertise to complete the process.
If you prefer a simpler approach, you can usually remove a computer virus by using an antivirus software program. For instance, Norton AntiVirus Basic can remove many infections that are on your computer. The product can also help protect you from future threats.
What does a computer virus do?
Some computer viruses are programmed to harm your computer by damaging programs, deleting files, or reformatting the hard drive. Others simply replicate themselves or flood a network with traffic, making it impossible to perform any internet activity. Even less harmful computer viruses can significantly disrupt your system’s performance, sapping computer memory and causing frequent computer crashes.
What are the symptoms of a computer virus?
Your computer may be infected if you recognize any of these malware symptoms:
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Slow computer performance
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Erratic computer behavior
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Unexplained data loss
1. ILOVEYOU
Perhaps the most virulent computer virus ever created, the ILOVEYOU virus managed to wreck PCs all across the world. Infecting almost 10% of the world’s PCs connected to the Internet, the virus caused a total damage of around $10 billion. The virus apparently got transmitted via email with a subject line “ILOVEYOU,” which is a radical human emotion that no one can ignore. To make it even more alluring, the email contained an attachment that read something like this: Love-Letter-For-You.TXT.vbs. The moment someone opened the file, the virus emailed itself to the first 50 contacts available in the PC’s Windows address book.
2. Melissa
Melissa became the breaking news on March 26, 1999, after hitting the new age of emailing. Built by David L, Melissa was spread in the form of an email attachment by the name “list.doc.” When a person clicked upon the attachment, the virus would find the Microsoft Outlook address book and email itself to the first 50 contacts on the list having a message “Here is that document you asked for…donot show anyone else.” Later on, FBI arrested David L and slapped him with a fine of $5000 for creating the wildest virus of its time.
3. My Doom
My Doom hit the malware world in 2004 and spread exponentially through email with random addresses of senders and subject lines. Infecting somewhere around two million PCs, My Doom smashed the cyber world by instigating a tremendous denial of service attack. It transmitted itself via email in a specially deceitful way that a receiver would first consider a bounced error message that read “Mail Transaction Failed.” However, as soon as the receiver clicked upon the message, the attachment executed and the worm transmitted to email addresses found in the user’s address book. It is easy to believe that this mass mailer worm caused a damage of almost $38 billion
4. Code Red
Taking advantage of the Microsoft Internet Information Server’s flaw, Code Red spread on the network servers in 2001. Here is an amusing fact about this dangerous virus—it didn’t need you to open an email attachment or execute a file; it just required an active Internet connection with which it ruined the Web page that you opened by displaying a text “Hacked by Chinese!” It’s no surprise that this virus devastated nearly $2.6 billion dollars by hitting almost one million PCs. And in less than a week’s time, the virus brought down over 400,000 servers that included the White House Web server as well.
5. Sasser
Sasser was a Windows worm that was discovered in 2004. Apparently, it would slow down and crash the PC, making it even hard to reset without cutting the power. And its effects were surprisingly troublesome as well, with millions of PCs being infected and crucial, significant infrastructure affected. The worm played on a buffer overflow susceptibility in Local Security Authority Subsystem Service (LSASS) that monitors the safety policy of local accounts causing crashes to the PC. The devastating effects of the virus were massive resulting in over a million infections. This included critical infrastructures, such as new agencies, hospitals, airlines, and public transportation.
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Frequent computer crashes