Definition of computer virus

A Trojan could be a seemingly benign file downloaded off the web or a Word doc attached to an email. Think that movie you downloaded from your favorite P2P sharing site is safe?

Think twice, because they could contain a virus. Is a worm a virus? Worms are not viruses, though the terms are sometimes used interchangeably. Even worse, the terms are sometimes used together in a strange and contradictory word salad; i. As mentioned earlier, a virus needs a host system to replicate and some sort of action from a user to spread from one system to the next. Once on a system, worms are known to drop malware often ransomware or open a backdoor.

Is ransomware a virus? Ransomware can be a virus. In fact, the very first ransomware was a virus more on that later. Nowadays, most ransomware comes as a result of computer worm, capable of spreading from one system to the next and across networks without user action e.

Is a rootkit a virus? Rootkits are not viruses. Is a software bug a virus? Software bugs are not viruses. A software bug refers to a flaw or mistake in the computer code that a given software program is made up of. Software bugs can cause programs to behave in ways the software manufacturer never intended. The Y2K bug famously caused programs to display the wrong date, because the programs could only manage dates through the year After the year rolled over like the odometer on an old car to While the Y2K bug was relatively harmless, some software bugs can pose a serious threat to consumers.

Cybercriminals can take advantage of bugs in order to gain unauthorized access to a system for the purposes of dropping malware, stealing private information, or opening up a backdoor. This is known as an exploit. Preventing computer viruses from infecting your computer starts with situational awareness. By staying on the lookout for phishing attacks and avoiding suspicious links and attachments, consumers can largely avoid most malware threats.

Regarding email attachments and embedded links, even if the sender is someone you know: viruses have been known to hijack Outlook contact lists on infected computers and send virus laden attachments to friends, family and coworkers, the Melissa virus being a perfect example. A simple call or text message can save you a lot of trouble.

Next, invest in good cybersecurity software. Antivirus AV refers to early forms of cybersecurity software focused on stopping computer viruses.

Just viruses. Given a choice between traditional AV with limited threat detection technology and modern anti-malware with all the bells and whistles, invest in anti-malware and rest easy at night.

As mentioned previously in this piece, traditional AV solutions rely on signature-based detection. AV scans your computer and compares each and every file against a database of known viruses that functions a lot like a criminal database. Going back to our virus analogy one final time—removing a virus from your body requires a healthy immune system. Same for your computer. A good anti-malware program is like having a healthy immune system. The free version of Malwarebytes is a good place to start if you know or suspect your computer has a virus.

Available for Windows and Mac, the free version of Malwarebytes will scan for malware infections and clean them up after the fact. Get a free premium trial of Malwarebytes for Windows or Malwarebytes for Mac to stop infections before they start.

You can also try our Android and iOS apps free to protect your smartphones and tablets. All the tactics and techniques employed by cybercriminals creating modern malware were first seen in early viruses. Things like Trojans, ransomware, and polymorphic code.

These all came from early computer viruses. To understand the threat landscape of today, we need to peer back through time and look at the viruses of yesteryear. Other notable firsts—Elk Cloner was the first virus to spread via detachable storage media it wrote itself to any floppy disk inserted into the computer. But a Scientific American article let the virus out of the lab.

In the piece, author and computer scientist A. Dewdney shared the details of an exciting new computer game of his creation called Core War. In the game, computer programs vie for control of a virtual computer. The game was essentially a battle arena where computer programmers could pit their viral creations against each other.

For two dollars Dewdney would send detailed instructions for setting up your own Core War battles within the confines of a virtual computer. What would happen if a battle program was taken out of the virtual computer and placed on a real computer system? In a follow-up article for Scientific American, Dewdney shared a letter from two Italian readers who were inspired by their experience with Core War to create a real virus on the Apple II. The brainchild of Pakistani brothers and software engineers, Basit and Amjad Farooq, Brain acted like an early form of copyright protection, stopping people from pirating their heart monitoring software.

Other than guilt tripping victims in to paying for their pirated software, Brain had no harmful effects. BHP also has the distinction of being the first stealth virus; that is, a virus that avoids detection by hiding the changes it makes to a target system and its files. The cover image depicted viruses as cute, googly eyed cartoon insects crawling all over a desktop computer.

Up to this point, computer viruses were relatively harmless. Yes, they were annoying, but not destructive. So how did computer viruses go from nuisance threat to system destroying plague?

The MacMag virus caused infected Macs to display an onscreen message on March 2, The infected Freehand was then copied and shipped to several thousand customers, making MacMag the first virus spread via legitimate commercial software product. The Morris worm knocked out more than 6, computers as it spread across the ARPANET , a government operated early version of the Internet restricted to schools and military installations. The Morris worm was the first known use of a dictionary attack.

As the name suggests, a dictionary attack involves taking a list of words and using it to try and guess the username and password combination of a target system. Robert Morris was the first person charged under the newly enacted Computer Fraud and Abuse Act , which made it illegal to mess with government and financial systems, and any computer that contributes to US commerce and communications. In his defense, Morris never intended his namesake worm to cause so much damage.

According to Morris, the worm was designed to test security flaws and estimate the size of the early Internet. A bug caused the worm to infect targeted systems over and over again, with each subsequent infection consuming processing power until the system crashed. Victims received a 5. Joseph L. 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. 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. All rights reserved. Firefox is a trademark of Mozilla Foundation. App Store is a service mark of Apple Inc. Alexa and all related logos are trademarks of Amazon.

Microsoft and the Window logo are trademarks of Microsoft Corporation in the U. The Android robot is reproduced or modified from work created and shared by Google and used according to terms described in the Creative Commons 3. Other names may be trademarks of their respective owners. No one can prevent all identity theft or cybercrime. Not all products, services and features are available on all devices or operating systems.

System requirement information on norton. The number of supported devices allowed under your plan are primarily for personal or household use only. Not for commercial use. Please login to the portal to review if you can add additional information for monitoring purposes. Security Center Malware What is a computer virus?

July 23, Join today. Cancel anytime. Start Free Trial. How does a computer virus attack? How do computer viruses spread? 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. Unusual activities like password changes. This could prevent you from logging into your computer.

How to help protect against computer viruses? How can you help protect your devices against computer viruses? Here are some of the things you can do to help keep your computer safe. What are the different types of computer viruses? Boot sector virus This type of virus can take control when you start — or boot — your computer.

Web scripting virus This type of virus exploits the code of web browsers and web pages. Direct action virus This type of virus comes into action when you execute a file containing a virus.