Computer virus article

Your mobile devices and smartphones can become infected with mobile viruses through shady app downloads. Viruses can hide disguised as attachments of socially shareable content such as funny images, greeting cards, or audio and video files.

This type of virus can take control when you start — or boot — your computer. One way it can spread is by plugging an infected USB drive into your computer. This type of virus exploits the code of web browsers and web pages.

If you access such a web page, the virus can infect your computer. A resident virus can execute anytime when an operating system loads. This type of virus comes into action when you execute a file containing a virus. Otherwise, it remains dormant. A polymorphic virus changes its code each time an infected file is executed.

It does this to evade antivirus programs. This common virus inserts malicious code into executable files — files used to perform certain functions or operations on a system. This kind of virus infects and spreads in multiple ways. It can infect both program files and system sectors. Macro viruses are written in the same macro language used for software applications.

Such viruses spread when you open an infected document, often through email attachments. You can take two approaches to removing a computer virus. One is the manual do-it-yourself approach. The other is by enlisting the help of a reputable antivirus program. 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.

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The two other main types are Trojans , which masquerade as harmless applications to trick users into executing them, and worms , which can reproduce and spread independently of any other application. 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. Remember, a virus can only execute and reproduce if its host application is running!

Still, with email such a common malware dispersal method, a question that causes many people anxiety is: Can I get a virus from opening an email? The answer is that you almost certainly can't simply by opening a message; you have to download and execute an attachment that's been infected with virus code. That's why most security pros are so insistent that you be very careful about executing email attachments, and why most email clients and webmail services include virus scanning features by default.

A particularly sneaky way that a virus can infect a computer is if the infected code runs as JavaScript inside a web browser and manages to exploit security holes to infect programs installed locally. Some email clients will execute HTML and JavaScript code embedded in email messages, so strictly speaking, opening such messages could infect your computer with a virus.

But most email clients and webmail services have built-in security features that would prevent this from happening, so this isn't an infection vector that should be one of your primary fears.

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The cost of computer attacks to companies is difficult to quantify precisely. One thing is certain, however: it is constantly improving.