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. Unlike a virus, it does not need to attach itself to an existing program. Worms spread by exploiting vulnerabilities in operating systems. Due to its replication nature it takes a lot of space in the hard drive and consumes more CPU uses which in turn makes the pc too slow also consumes more network bandwidth.
Macro Virus: These type of virus infects word, excel, PowerPoint, access and other data files. Once infected repairing of these files is very much difficult. Master boot record files: MBR viruses are memory-resident viruses and copy itself to the first sector of a storage device which is used for partition tables or OS loading programs. A MBR virus will infect this particular area of Storage device instead of normal files.
These are also memory resident in nature. As soon as the computer starts it gets infected from the boot sector. Cleaning this type of virus is very difficult. They infect program files and when the infected program is executed, these viruses infect the boot record.
When you boot the computer next time the virus from the boot record loads in memory and then start infecting other program files on disk. Polymorphic viruses: A virus that can encrypt its code in different ways so that it appears differently in each infection. These viruses are more difficult to detect. Stealth viruses: These types of viruses use different kind of techniques to avoid detection.
For example, the Whale virus adds bytes to an infected file; then the virus subtracts the same number of bytes from the size given in the directory.
Generically adware is a software application in which advertising banners are displayed while any program is running. Adware can automatically get downloaded to your system while browsing any website and can be viewed through pop-up windows or through a bar that appears on a computer screen automatically.
Adwares are used by companies for marketing purpose. A cookie is a plain text file that is stored on your computer in a cookies folder and it stores data about your browsing session. Cookies are used by many websites to track visitor information A tracking cookie is a cookie which keeps tracks of all your browsing information and this is used by hackers and companies to know all your personal details like bank account details, your credit card information etc. Spamming is a method of flooding the Internet with copies of the same message.
Most spams are commercial advertisements which are sent as an unwanted email to users. Spams are also known as Electronic junk mails or junk newsgroup postings.
Download Malwarebytes free to scan your computer. Cybersecurity Basics. Computer Virus. 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. Asurion Experts help millions of customers get the most out of their tech and resolve their device problems. A computer virus is a malicious program—or form of malware—that's designed to disrupt your computer and spread to other devices. It attaches itself to a valid program, alters the code, then replicates itself to infect other files or systems.
A virus can destroy data or cause your machine to stop working. Your computer can get a virus in many ways. The most common ones are:. Think your Mac or PC may have a virus? Look for these 10 telltale signs:. Macs have built-in protections for viruses and malware, so it's uncommon for them to become infected.
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