Different causes of computer viruses

A computer virus is a small software program that spreads from one computer to another and interferes with computer operation. A computer virus might corrupt or delete data on a computer, use an email program to spread the virus to other computers, or even delete everything on the hard disk.

Computer viruses are frequently spread by attachments in email messages or by instant messaging messages. Therefore, you must never open an email attachment unless you know who sent the message or you are expecting the email attachment.

Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files. Computer viruses also spread through downloads on the Internet. They can be hidden in pirated software or in other files or programs that you might download. Tip: For information about the symptoms of a computer virus, go to the Microsoft PC Security website.

A worm is computer code that spreads without user interaction. Most worms begin as email attachments that infect a computer when they're opened. The worm scans the infected computer for files, such as address books or temporary webpages, that contain email addresses. The worm uses the addresses to send infected email messages, and frequently mimics or spoofs the "From" addresses in later email messages so that those infected messages seem to be from someone you know.

Worms then spread automatically through email messages, networks, or operating system vulnerabilities, frequently overwhelming those systems before the cause is known. Worms aren't always destructive to computers, but they usually cause computer and network performance and stability problems. A trojan horse is a malicious software program that hides inside other programs. It enters a computer hidden inside a legitimate program, such as a screen saver. Then it puts code into the operating system that enables a hacker to access the infected computer.

Trojan horses do not usually spread by themselves. They are spread by viruses, worms, or downloaded software. Spyware can install on your computer without your knowledge. Spyware can track Internet search habits and can also redirect your web browser to a different website than you intend to go to.

A rogue security software program tries to make you think that your computer is infected by a virus and usually prompts you to download or buy a product that removes the virus. The names of these products frequently contain words like Antivirus, Shield, Security, Protection, or Fixer.

This makes them sound legitimate. They frequently run right after you download them, or the next time that your computer starts. Rogue security software can prevent applications, such as Internet Explorer, from opening.

Rogue security software might also display legitimate and important Windows files as infections. Typical error messages or pop-up messages might contain the following phrases:. Do not click anything inside the dialog box. One thing to keep in mind about viruses is that they generally exploit vulnerabilities in your operating system or application code in order to infect your systems and operate freely; if there are no holes to exploit, you can avoid infection even if you execute virus code.

To that end, you'll want to keep all your systems patched and updated, keeping an inventory of hardware so you know what you need to protect, and performing continuous vulnerability assessments on your infrastructure. How can you tell if a virus has slipped past your defenses? With some exceptions, like ransomware, viruses are not keen to alert you that they've compromised your computer. Just as a biological virus wants to keep its host alive so it can continue to use it as a vehicle to reproduce and spread, so too does a computer virus attempt to do its damage in the background while your computer still limps along.

But there are ways to tell that you've been infected. Norton has a good list ; symptoms include:. If you suspect your computer has been infected, a computer virus scan is in order. There are plenty of free services to start you on your exploration: The Safety Detective has a rundown of the best. Once a virus is installed on your computer, the process of removing it is similar to that of removing any other kind of malware — but that isn't easy. CSO has information on how to remove or otherwise recover from rootkits , ransomware , and cryptojacking.

We also have a guide to auditing your Windows registry to figure out how to move forward. If you're looking for tools for cleansing your system, Tech Radar has a good roundup of free offerings , which contains some familiar names from the antivirus world along with newcomers like Malwarebytes. And it's a smart move is to always make backups of your files , so that if need be you can recover from a known safe state rather than attempting to extricate virus code from your boot record or pay a ransom to sketchy Eastern European gangsters.

The first true computer virus was Elk Cloner , developed in by fifteen-year-old Richard Skrenta as a prank.

Elk Cloner was an Apple II boot sector virus that could jump from floppy to floppy on computers that had two floppy drives as many did. Every 50th time an infected game was started, it would display a poem announcing the infection.

But most of the big-name malware you've heard of in the 21st century has, strictly speaking, been worms or Trojans, not viruses. That doesn't mean viruses aren't out there, however — so be careful what code you execute.

Prion Protein. Hand Drawn Dungeon Maps. Dc Power Supply Circuit Diagram. P Or Q Truth Table. Hacker Team.

Minecraft Error. Toothless Stitch Drawings. Commercial Pellet Smokers For Restaurants. Soundcloud Go. Blue Curacao Drink Recipes. Run With Graphics Processor. For Home View all Malwarebytes products. A computer virus is a type of malware that attaches to another program like a document , which can replicate and spread after a person first runs it on their system.

For instance, you could receive an email with a malicious attachment, open the file unknowingly, and then the computer virus runs on your computer. Viruses are harmful and can destroy data, slow down system resources, and log keystrokes. Viruses and malware continue to evolve, and often cybercriminals use the type that gives them the best return at that particular time. While a computer virus is a type of malware, not all malware are computer viruses. The easiest way to differentiate computer viruses from other forms of malware is to think about viruses in biological terms.

Take the flu virus, for example. The flu requires some kind of interaction between two people—like a hand shake, a kiss, or touching something an infected person touched. Worms, on the other hand, are able to spread across systems and networks on their own, making them much more prevalent and dangerous.

Famously, the WannaCry ransomware worm spread around the world, took down thousands of Windows systems, and raked in an appreciable amount of untraceable Bitcoin ransom payments for the alleged North Korean attackers. They are still a harmful type of malware, but they are not the only type of threat out there today, on your computer or mobile device. Many computer viruses target systems running Microsoft Windows.

Macs, on the other hand, have enjoyed a reputation as virus-proof super machines, but in Apple's own admission, Macs do get malware. There are more Windows users in the world than Mac user s and cybercriminals simply choose to write viruses for the operating system OS with the largest amount of potential victims.

Today, the "computer" in our pockets may be the one we use most often: our smartphones. Android and iOS are susceptible to various forms of malware, too. Fortunately, most cybersecurity companies like Malwarebytes offer protection for Windows, Mac, Android, and iOS today. What fun! Is a Trojan a virus? Trojans can be viruses.

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.