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Please note: Do not post advertisements, offensive material, profanity, or personal attacks. Please remember to be considerate of other members. All submitted content is subject to our Terms Of Use. General discussion. How does one create a computer virus? A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well. We'll take a closer look at how a worm works in the next section.
Ads by Google. How Firewalls Work. How E-mail Works. How Spyware Works. Antivirus Software Reviews. Web Filtering Reviews. How do you protect against computer viruses? How Computer Viruses Work If you've had a computer for any long period of time, you've probably encountered a computer virus.
Find out exactly what they are, and how they work in this HowStuffWorks video. Complete solution that works! Read reviews. Free 30 days full version trial www. One such trick is the ability to load viruses into memory so they can keep running in the background as long as the computer remains on. This gives viruses a much more effective way to replicate themselves. Another trick is the ability to infect the boot sector on floppy disks and hard disks.
The boot sector is a small program that is the first part of the operating system that the computer loads. It contains a tiny program that tells the computer how to load the rest of the operating system.
By putting its code in the boot sector, a virus can guarantee it's executed. It can load itself into memory immediately, and run whenever the computer is on. Boot sector viruses can infect the boot sector of any floppy disk inserted in the machine, and in places like college campuses, where lots of people share machines, they can spread like wildfire.
In general, neither executable nor boot sector viruses are very threatening today. The first reason for their decline has been the huge size of today's programs. Most programs you buy today come on compact discs. Commercially distributed compact discs CDs cannot be modified, and that makes viral infection of a CD unlikely, unless the manufacturer permits a virus to be burned onto the CD during production.
People certainly can't carry applications around on floppy disks like they did in the s, when floppies full of programs were traded like baseball cards. Boot sector viruses have also declined, because operating systems now routinely protect the boot sector. Infection from boot sector viruses and executable viruses is still possible.
Even so, it's a lot less likely than it once was. Call it "shrinking habitat," if you want to use a biological analogy. The environment of floppy disks, small programs and weak operating systems made these viruses possible in the s, but that environmental niche has been largely eliminated by huge executables, unchangeable CDs and better operating system safeguards.
Virus authors adapted to the changing computing environment by creating the e-mail virus. For example, the Melissa virus in March was spectacular in its attack. Melissa spread in Microsoft Word documents sent via e-mail , and it worked like this:. Someone created the virus as a Word document and uploaded it to an Internet newsgroup. Anyone who downloaded the document and opened it would trigger the virus. The virus would then send the document and therefore itself in an e-mail message to the first 50 people in the person's address book.
The e-mail message contained a friendly note that included the person's name, so the recipient would open the document, thinking it was harmless.
The virus would then create 50 new messages from the recipient's machine. At that rate, the Melissa virus quickly became the fastest-spreading virus anyone had seen at the time.
As mentioned earlier, it forced a number of large companies to shut down their e-mail systems to control the spread. It contained a piece of code as an attachment. People who double-clicked on the attachment launched the code. It then sent copies of itself to everyone in the victim's address book and started corrupting files on the victim's machine. This is as simple as a virus can get. It is really more of a Trojan horse distributed by e-mail than it is a virus. It is a complete programming language and it can be used to write programs that do things like modify files and send e-mail messages.
It also has a useful but dangerous auto-execute feature. A programmer can insert a program into a document that runs instantly whenever the document is opened. This is how the Melissa virus was programmed. Anyone who opened a document infected with Melissa would immediately activate the virus. DOT so that any file saved later would also contain the virus.
It created a huge mess. Microsoft applications have a feature called Macro Virus Protection built into them to prevent this sort of virus. With Macro Virus Protection turned on the default option is ON , the auto-execute feature is disabled.
So, when a document tries to auto-execute viral code, a dialog pops up warning the user. Unfortunately, many people don't know what macros or macro viruses are, and when they see the dialog they ignore it, so the virus runs anyway. Many other people turn off the protection mechanism. Because of this, the Melissa virus spread despite the safeguards in place to prevent it.
If a person double-clicked on the program that came as an attachment, then the program ran and did its thing. What fueled this virus was the human willingness to double-click on the executable. Commandeered accounts will send out links to viruses in instant messages; anyone who clicks the link and installs a Trojan application will have their own account hijacked and unwittingly spam their own friends with the compromising link.
While you may be taking steps to protect your computer from becoming infected by a virus, you may very well run into another, more insidious type of attack. Phishing and other social engineering attacks have been on the rise. Social engineering is a fancy term for someone trying to get you to give up your personal information -- online or in person -- so they can use it to steal from you.
Anti-spam traps may catch e-mail messages coming from phishers, but the U. Computer Emergency Readiness Team says the best way for you to beat them at their own game is to be wary. And never give out your personal or financial information online.
A worm is a computer program that has the ability to copy itself from machine to machine. Worms use up computer processing time and network bandwidth when they replicate, and often carry payloads that do considerable damage.
A worm called Code Red made huge headlines in Experts predicted that this worm could clog the Internet so effectively that things would completely grind to a halt. A worm usually exploits some sort of security hole in a piece of software or the operating system.
Wired magazine took a fascinating look inside Slammer's tiny byte program. 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. 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.
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