Once a computer virus is running, it can infect other programs or documents. Obviously, the analogy between computer and biological viruses stretches things a bit, but there are enough similarities that the name sticks.
People write computer viruses. A person has to write the code, test it to make sure it spreads properly and then release it. A person also designs the virus's attack phase, whether it's a silly message or the destruction of a hard disk. Why do they do it? There are at least four reasons. The first is the same psychology that drives vandals and arsonists. Why would someone want to break a window on someone's car, paint signs on buildings or burn down a beautiful forest? For some people, that seems to be a thrill.
If that sort of person knows computer programming, then he or she may funnel energy into the creation of destructive viruses. The second reason has to do with the thrill of watching things blow up.
Some people have a fascination with things like explosions and car wrecks. When you were growing up, there might have been a kid in your neighborhood who learned how to make gunpowder. And that kid probably built bigger and bigger bombs until he either got bored or did some serious damage to himself. Creating a virus is a little like that -- it creates a virtual bomb inside a computer, and the more computers that get infected, the more "fun" the explosion. The third reason involves bragging rights.
Sort of like Mount Everest -- the mountain is there, so someone is compelled to climb it. If you are a certain type of programmer who sees a security hole that could be exploited, you might simply be compelled to exploit the hole yourself before someone else beats you to it. And then there's cold, hard cash. Viruses can trick you into buying fake software, steal your personal information and use it to get to your money, or be sold on the digital equivalent of the black market.
Powerful viruses are valuable -- and potentially lucrative -- tools. Of course, most virus creators seem to miss the point that they cause real damage to real people with their creations. Destroying everything on a person's hard disk is real damage. Forcing a large company to waste thousands of hours cleaning up after a virus attack is real damage. Even a silly message is real damage because someone has to waste time getting rid of it.
For this reason, the legal system continues to develop more rigorous penalties for people who create viruses. On the second Tuesday of every month, Microsoft releases a list of known vulnerabilities in the Windows operating system. The company issues patches for those security holes at the same time, which is why the day is known as Patch Tuesday.
Viruses written and launched on Patch Tuesday to hit unpatched systems are known as "zero-day" attacks. Thankfully, the major anti-virus vendors work with Microsoft to identify holes ahead of time, so if you keep your software up to date and patch your system promptly, you shouldn't have to worry about zero-day problems. Traditional computer viruses were first widely seen in the late s, and came about because of several factors.
The first factor was the spread of personal computers PCs. Prior to the s , home computers were nearly non-existent. Real computers were rare, and were locked away for use by "experts. By the late s, PCs were in businesses, homes and college campuses. The second factor was the use of computer bulletin boards. People could dial up a bulletin board with a modem and download programs of all types.
Games were extremely popular, and so were simple word processors, spreadsheets and other productivity software. Bulletin boards led to the precursor of the virus known as the Trojan horse. A Trojan horse masquerades as a program with a cool-sounding name and description, enticing you to download it. When you run the program, however, it does something uncool, like erasing your hard drive. You think you're getting a neat game, but instead, you get a wiped-out system. Trojan horses only hit a small number of people because they're quickly discovered, and word of the danger spreads among users.
The third factor that led to the creation of viruses was the floppy disk. In the s, programs were small, and you could fit the entire operating system , a few programs and some documents onto a floppy disk or two. Many computers did not have hard disks, so when you turned on your machine it would load the operating system and everything else from the floppy disk.
Virus authors took advantage of this to create the first self-replicating programs. Early viruses were pieces of code embedded in a larger, legitimate program, such as a game or word processor. If it can find one, it modifies the program to add the virus's code into that program. Then the virus launches the "real program. Unfortunately, the virus has now reproduced itself, so two programs are infected.
The next time the user launches either of those programs, they infect other programs, and the cycle continues. If one of the infected programs is given to another person on a floppy disk, or if it is uploaded so other people can download it, then other programs get infected.
This is how the virus spreads -- similar to the infection phase of a biological virus. But viruses wouldn't be so violently despised if all they did was replicate themselves. Most viruses also have a destructive attack phase where they do real damage. Some sort of trigger will activate the attack phase, and the virus will then do something -- anything from displaying a silly message on the screen to erasing all of your data.
The trigger might be a specific date, a number of times the virus has been replicated or something similar. Virus creators have added new tricks to their bag throughout the years.
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. Mimiviruses are different from viruses in that they have way more genes than other viruses, including genes with the ability to replicate and repair DNA.
The pandoravirus, discovered in , is even larger than the mimivirus and has approximately genes, with 93 percent of their genes not known from any other microbe. The pithovirus was discovered in from a Siberian dirt sample that had been frozen for 30, years.
However, the pithovirus possesses some replication machinery of its own. While it contains fewer genes than the pandoravirus, two-thirds of its proteins are unlike those of other viruses.
Tupanvirus was discovered in Brazil. It holds an almost nearly complete set of genes necessary for protein production. The discoveries of these giant viruses and others not listed here have made some researchers suggest they lie somewhere between bacterium and viruses, and might even deserve their own branch on the Tree of Life.
This would create a yet undescribed fourth domain of life aside from Bacteria, Archaea, and Eukaryotes. You only need to worry if you happen to be an amoeba. In our next posting about viruses , we'll look at how they might be the most successful of earth's inhabitants. Arnold, Carrie. National Geographic. The distinguishing feature of a virus is that it needs to infect other programs to operate.
Imagine an application on your computer has been infected by a virus. We'll discuss the various ways that might happen in a moment, but for now, let's just take infection as a given. How does the virus do its dirty work? Bleeping Computer provides a good high-level overview of how the process works. The general course goes something like this: the infected application executes usually at the request of the user , and the virus code is loaded into the CPU memory before any of the legitimate code executes.
At this point, the virus propagates itself by infecting other applications on the host computer, inserting its malicious code wherever it can. A resident virus does this to programs as they open, whereas a non-resident virus can infect executable files even if they aren't running.
Boot sector viruses use a particularly pernicious technique at this stage: they place their code in the boot sector of the computer's system disk, ensuring that it will be executed even before the operating system fully loads, making it impossible to run the computer in a "clean" way.
Once the virus has its hooks into your computer, it can start executing its payload, which is the term for the part of the virus code that does the dirty work its creators built it for.
These can include all sorts of nasty things: Viruses can scan your computer hard drive for banking credentials, log your keystrokes to steal passwords, turn your computer into a zombie that launches a DDoS attack against the hacker's enemies, or even encrypt your data and demand a bitcoin ransom to restore access.
Other types of malware can have similar payloads, of course: there are ransomware worms and DDoS Trojans and so forth. In the early, pre-internet days, viruses often spread from computer to computer via infected floppy disks.
The SCA virus, for instance, spread amongst Amiga users on disks with pirated software. Today, viruses spread via the internet. In most cases, applications that have been infected by virus code are transferred from computer to computer just like any other application. Because many viruses include a logic bomb — code that ensures that the virus's payload only executes at a specific time or under certain conditions — users or admins may be unaware that their applications are infected and will transfer or install them with impunity.
Infected applications might be emailed inadvertently or deliberately — some viruses actually hijack a computer's mail software to email out copies of themselves ; they could also be downloaded from an infected code repository or compromised app store.
One thing you'll notice that all of these infection vectors have in common is that they require the victim to execute the infected application or code. The Michelangelo virus was a destructive worm that would spread onto any floppy disk inserted into the computer, while remaining dormant and undetectable. But then on the titular painter's birthday, March 6th, it would activate and absolutely ruin any computer infected with it.
While there was nothing especially unique about the Michelangelo virus, it was soon discovered that a few computer and software manufacturers accidentally shipped products with Michelangelo pre-installed onto them.
The actual number of infected computers was never more than 20, But John McAfee, founder of McAfee antivirus and… interesting fellow, made the expert claim that hundreds of thousands, if not millions of machines were infected. Which may have been a motivating factor in him riling up the public.
The document, which was a DOC file, included a list of 80 pornographic websites as well as usernames and passwords to access each one which must have been confusing to get from Grandpa.
This meant that oftentimes classified or private files would be shared with friends, family, or work associates. Melissa would be contained fairly quickly, and its creator arrested, but perhaps its most important legacy is how it directly inspired one of the biggest malware attacks even to this day, ILOVEYOU , or the Love Letter worm.
Sent through an email disguised as a love letter, ILOVEYOU's attack would begin upon the opening of the attached text file, unleashing a worm that would cause far more damage than your typical worm — even compared to the malware of today.
ILOVEYOU would download a Trojan as soon as it was activated, which would then overwrite files, steal user data such as usernames, passwords, IP addresses , and more, then send itself to everyone on your email contact list. Then, it would effectively lock you out of your own email address. Not only to the impact malware could have on the unprotected, uninformed masses, but also all the things malware was capable of doing given enough free reign. Companies who had long since viewed security as a secondary concern started shifting priorities, and antivirus products , once seen as a nice luxury, became absolutely essential.
But just as there are brilliant hackers who are trying to steal from you, there are just as many brilliant cybersecurity researchers who are working to keep you safe with products like AVG.
So as long as you pay attention, keep your antivirus updated , and continue to learn more about cybersecurity, you can feel secure every time you log on.
Get it for Android , iOS , Mac. Get it for Mac , PC , Android. To learn more about viruses, and to make sure your devices remain virus-free, check out our detailed guides:. How to know if your phone has a virus and how to get rid of it. How to remove a virus from your computer.
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