How do computer viruses work?

Are you concerned that your computer may have a virus? If your computer is infected, learning how to get rid of a computer virus is vital.

This article teaches you all there is to know about how computer viruses work and computer virus removal.

Read on as we discuss:

• How to get rid of a computer virus.
• What a computer virus is.
• How to tell if your computer has a virus.
• Whether your computer can become infected with a virus via email.
• How to protect your computer from viruses.

How to get rid of a computer virus

In this section, we explore how to get rid of a computer virus from a PC and from a Mac.

Removing a computer virus from a PC

Computer viruses are almost always invisible. Without anti-virus protection, you may not know you have one. This is why it is vital to install anti-virus protection on all your devices.

If your PC has a virus, following these ten simple steps will help you to get rid of it:

Step 1: Download and install a virus scanner

Download a virus scanner or complete internet security solution. We recommend Kaspersky Internet Security. The video below will guide you through the installation process:

Step 2: Disconnect from internet

When you are removing a virus from your PC, it is a good idea to disconnect from the internet to prevent further damage: some computer viruses use the internet connection to spread.

Step 3: Reboot your computer into safe mode

To protect your computer while you remove the virus, reboot it in ‘Safe Mode’. Are you unsure of how to do this?

Here is a simple guide:

• Turn your computer off and on again
• When the screen lights, press F8 to bring up the ‘Advanced boot options’ menu
• Click ‘Safe Mode with Networking’
• Remain disconnected from the internet

Step 4: Delete any temporary files

Next, you need to delete any temporary files using ‘Disk Clean Up’.

Here’s how to do this:

• Click the Windows logo on the right bottom
• Type “Temporary Files”
• Choose “Free up disk space by deleting unnecessary files”
• Find and select “Temporary Internet Files” in the ‘Files to delete’ Disk Cleanup list and click OK
• Confirm “Delete Files” selection

Some viruses are programmed to initiate when your computer boots up. Deleting temporary files may delete the virus. However, it is not safe to rely on this. To ensure you rid your computer of viruses, it is wise to complete the following steps.

Step 5: Run a virus scan

Now it is time to run a virus scan using your chosen anti-virus or internet security software. If you are using Kaspersky Internet Security, select and run ‘Scan’.

Step 6: Delete or quarantine the virus

If a virus is found, it may affect multiple files. Select ‘Delete’ or ‘Quarantine’ to remove the file(s) and get rid of the virus. Rescan your computer to check there’s no further threats. If threats are found, quarantine or delete the files.

Step 7: Reboot your computer

Now that the virus is removed, you can reboot your computer. Simply turn it on as you would normally. It no longer needs to be in ‘Safe Mode’.

Step 8: Change all your passwords

To protect your computer from further attack, change all your passwords in case they were compromised. This is only strictly necessary if you have reason to believe your passwords have been captured by malware, but it is better to be safe than sorry.

You can always check the virus’s functionality on your anti-virus vendor’s website or with their technical support team if unsure.

Step 9: Update your software, browser and operating system

Updating your software, browser and operating system will reduce the risk of flaws in old code being exploited by criminals to install malware on your computer.

Removing a computer virus from a Mac

If you use a Mac, you may be under the impression that your computer cannot get a virus. Unfortunately, this is a misconception. There are fewer viruses that target Macs compared with the many that target PCs, but Mac viruses do exist.

Some Mac viruses are designed to trick users into thinking they are anti-virus products. If you accidentally download one of these, your computer may be infected. Three examples of Mac viruses of this type are ‘MacDefender’, ‘MacProtector’, and ‘MacSecurity’.

If you think your Mac has a virus, here are six steps to follow to remove it:

• Quit the application or software that seems to be affected.
• Go to ‘Activity monitor’ and search for known Mac viruses such as ‘MacDefender’, ‘MacProtector’, or ‘MacSecurity’.
• If you find one of these viruses, click ‘Quit process’ before quitting ‘Activity monitor’.
• Next, go to your ‘Applications’ folder and drag the file into your ‘Trash’.
• Remember to empty the ‘Trash’ folder afterwards to permanently delete the virus.
• Now make sure your software and apps are up to date to benefit from the latest security patches.

To ensure nothing is missed and to keep your Mac protected, consider installing a running an anti-virus solution if you do not already have one. We recommend comprehensive internet security solution like Kaspersky Total Security.

What is a computer virus?

A computer virus is a type of malware (malicious software) designed to make self-replicate, i.e. to make copies of itself on any drive connected to your computer.

Computer viruses are so-called because, like real viruses, they can self-replicate. Once your computer is infected with a virus, this is how it spreads. When a computer virus infects your computer, it may slow it down and stops it working properly.

There are three main ways that your computer may have become infected with a computer virus.

The first way your computer could become infected from removable media, like a USB stick. If you insert a USB stick or disk into your computer from an unknown source, it may contain a virus.

Sometimes hackers leave infected USB sticks or disks in people’s workplaces, or public places like cafes to spread computer viruses. People sharing USBs may also transfer files from an infected computer to one that isn’t infected.

Another way your computer become infected with a virus is through a download from the internet.

If you are downloading software or apps to your computer, ensure you do so from a trusted source. For example, the Google Play Store or Apple’s App Store. Avoid downloading anything via a pop-up or a website you do not know.

The third way your computer could become infected with a virus is if you open an attachment, or click on a link, in a spam email.

Whenever you receive mail from a sender you do not know or trust, avoid opening it. If you do open it, do not open any attachments or click on any links.

How to tell if your computer has a virus

There are numerous signs to look out for that indicate your computer may have a virus.

Firstly, is your computer slowing down? If everything is taking longer than usual, your computer may have become infected.

Secondly, look out for apps or programs that you do not recognize. If you see an app or a program appear on your computer that you do not remember downloading, exercise caution.

It is a good idea to uninstall any software you do not recognize and then to run a virus scan using anti-virus or internet security software to check for threats. Pop-ups that appear when your browser is closed are a tell tail sign of a virus. If you see these, take immediate action to remove the virus, by following the steps outlined above.

Another sign that your computer may have a virus is if apps or programs on your computer start behaving strangely. If they start crashing for no apparent reason, your computer may have a virus.

Finally, a virus may cause your computer to start overheating. If this happens, investigate whether you have a virus using anti-virus or internet security software.

Can your computer become infected with a virus via email?

Your computer can become infected with a virus via email, but only if you open attachments within a spam email or click on the links contained in them.

Simply receiving a spam email will not infect your computer. Just mark these as spam or junk and ensure they are deleted. Most email providers will automate this (Gmail for example) but if any slip through the net, just mark them as spam yourself and don’t open them.

How to protect your computer from viruses

Here are some key ways that you can protect your computer from viruses:

• Use anti-virus software or a complete internet security solution, like Kaspersky Total Security. For your Android mobile, consider Kaspersky Internet Security for Android.
• Research apps and software by reading user reviews.
• Read developer descriptions before you download apps and software.
• Only download apps and software from trusted sites.
• Check how many downloads apps and software have. The more, the better.
• Check what permissions apps and software ask for. Are these reasonable?
• Never click on unverified links in spam emails, messages or unfamiliar websites.
• Do not open attachments in spam emails.
• Keep software, apps and your operating system updated.
• Use a secure VPN connection for public Wi-Fi, like Kaspersky Secure Connection.
• Never insert unknown USB sticks or disks into your computer.

How do computer viruses work?

Has your computer got a virus? Learn how to get rid of a computer virus, how to find out if your computer has one and if you can get a computer virus via email.

Popular Types of Computer Viruses

Computer viruses can wreck havoc to the operations of the computer. A computer virus is a type of malware that is intentionally written to gain entry into your computer, without your knowledge or permission. It has the capacity to modify or replicate itself, in which case it will continue spreading. There are varying different types of computer viruses and their effects also vary widely. While some simply replicate themselves, others adversely affect the programs and consequently, the system’s performance. This therefore underlines the importance of not assuming that the virus is harmless and leaving it in the system. It is important that you scan your computer for viruses once in a while, so that you can be sure about its protection.

There are various types of computer viruses, classified in terms of techniques, origin, the types of files affected, damage, OS or Platform attacked, as well as the places they hide. It’s relatively hard to answer how many different types of computer viruses there are but below covers the main core concepts of the common types:

Resident viruses: These are permanent viruses dwelling in RAM memory. In this case, they would be in a position to overcome, as well as interrupt, all operations that the system executes. Their effects include corrupting programs and files that are closed, opened, renamed or copied.

Overwrite viruses: These viruses delete information that is in the infected files. In this case, the infected files would be rendered totally or partially useless. Unfortunately, you would only clean the infected file by deleting it completely, therefore losing original content.

Direct action viruses: This virus replicates itself, then acts when executed. Subject to satisfaction of particular conditions, the virus infects files located in the folders or computer directory. It is also in directories specified in the AUTOEXEC.BAT PATH. In most cases, it is located in hard drive’s root directory and takes particular action when the computer boots.

File infectors: This virus infects executable files or programs. On running the programs, the virus would be activated, then be able to carry out its damaging effects. Most of the existing viruses are in this category.

Boot viruses: This virus infects the hard disk’s or floppy drive’s boot sector. This would make the computer unable to boot. These viruses can, however, be avoided by ensuring that the floppy disks and hard drive is well protected. Never start the computer using an unknown disk drive or floppy disk.

Directory viruses: This virus alters the paths indicating a file’s location. In this case, when the infected program is executed, you will be running the program unknowingly, since the virus has moved the original program and file to another location. This therefore makes it impossible to locate the moved files.

Macro virus: This virus affects files created using particular programs or applications containing macros. The mini-programs increase their ability to automate some operations, in which case they would be performed as single actions. The user would therefore be saved the trouble of executing them singularly.

E-Mail Virus: Worth listing even if most are Macro viruses. Generally these kinds of viruses infect computers through social interaction with someone who e-mails the end user. They may be asked to verify a billing statement or look at an invoice attachement. Upon opening the attachment the macro is fired off and runs and infected the computer. Most macro viruses are easily stopped by simply keeping software up to date on computers.

Ransomware: Ransomware is type of malicious software product that attempts to hold a computer for ransom. This might be locking files, hiding files, changing permissions on files or encrypting files.

In early ransome attacks files where often simply hidden from the viewers and a monetary payment was requested to un-do the changes. This kind of attack was rather simple to resolve by doing a system restore to un-do the changes to those files.

As Ransomware evolved they started to encrypt files from users which no system restore would be able to resolve. The core Windows files would be fully functional but personal files and folders would be changed leaving the end user with no access to those files unless a payment was sent to the make of the ransomware software.

As Crypto currencies such as Bitcoin arrived on the market ransomware became more prevalent as makers could have people send them bitcoin to a wallet address which they then could send out to multiple wallets and make the tracing of the coins hard to follow.

With the release of NAS hacking tools on the black market an increase in sophisticated ransomware attacks occurred in early 2017 including the wannaCry https://en.wikipedia.org/wiki/WannaCry_ransomware_attack attack which affected hundreds of companies around the world including government agencies such as the British National Health Service.

Browser Highjacks: The most common types of viruses seen in 2014 – 2015 that have a high impact on users are Browser Highjack viruses. Generally this type of infection is not really a virus but something called PUP or Potentially unwanted software. In most cases these browser highjacks change the users home page and search settings in the web browser and often make it extremely hard to remove and restore the default settings. Often times these kinds of browser highjacks get installed from bundled software that may include free programs such as computer games or wall papers.

First Known Computer Virus

The first known computer virus appeared in 1971 and was called the Creeper virus. This specific virus targeted select main frame computers running TENEX.

To delete this virus a program was created by Ray Tomlinson called the Reaper which was actually another virus whose sole purpose was to delete the Creeper virus. Essentially this was the second known computer virus but some also refer to it as the first anti-virus client.

John McAfee released the first version of a Virus Scanner in 1987 which kicked off the creation of McAfee antivirus.

Virus Prevention

The only solution to never risk getting a computer virus is to keep the computer disconnected from the internet and off which is not practical.

That being said you have many options that can greatly reduce the risk of getting a computer virus.

1. Keep your operating system up to date. Microsoft, Apple and Linux have updates that roll out on a regular basis. Keeping your operating system up to date alone will stop the vast majority of known threats.

The Wanna Cry ransomware is a good example of this. System affected by this virus were those running Windows XP which stopped having updates to the program because of newer replacements such as Vista, Windows 7, Windows 8 and Windows 10.

1. Keep your web browser updated. Nearly all web browsers have an auto update feature that allows you to auto update your web browser. Popular browsers out there include, FireFox, Chrome, Safari and Edge (formerly known as Internet Explorer)
2. Keep your software programs updated. Programs such as Office, Adobe PDF, Flash are all targeted programs due to their wide user base. The more popular a program is the more it’s a target for exploits.
3. Safe Web Browsing. This is covered more in-depth in the Safe Web Browsing section. Basically don’t un-trusted websites and you will be 99% of the way there.
4. Have an Active antivirus client installed that prevents virus infections and keep the program updated.
5. Do not open e-mails with attachments from unknown senders. Even if it’s a know use caution as their e-mail could of been hacked.

Anti-Virus Software Downloads

There are a wide range of free anti-virus clients on the market

Free Software Downloads

Many other free programs exist on the market such as Avast and AVG. They have light virus protection which does protect end users from most basic threats.

There are of course many paid antivirus clients that do a fantastic job at protecting computers such as Norton, Trend Micro, Kaspersky, McAfee, G-data and on and on.

There are also different tiers of protection within different antivirus clients. A general antivirus client will offer protection from virus and malware while an Internet Security Suit generally with include more robust security measures like a firewall, e-mail scanner and possibly a data backup solution like what is included in the Norton 360 security suite.

Virus Removal Options

Hiring Someone

The first more obvious one is hiring a professional to remove the virus for you. This can be a local repair shop or a remote computer repair company that can remote into your PC to remove the computer virus for you.

In most cases these specialist will use freely available computer repair programs to scan your computer. Manual removal is seldom needed unless there is a core file that an anti-virus program cannot detect and the professional can isolate the file and delete it manually.

The added benefit to hiring a computer repair company is the peace of mind knowing the virus is fully removed from the computer.

Using Anti-virus Software

Most people can still install software even when infected with a computer virus. Installing and running a full deep scan of a computer with anti-virus software that is updated often times will remove a computer virus.

Virus Related Scams

Virus related scams have been around for over a decade.

A common scam is simply showing the end user a webpage that tells the user they have a computer virus. Scary wording is often used in an attempt to trick the user into panicking and then making a purchase. Simply closing down the web browser would stop the error messages.

You now see this commonly played out on mobile devices with ads that say the user has several viruses found on their phone and they need to install an app to protect their phone. The app is there simply to push ads constantly when you are browsing the web.

Another popular scam going around where from fake antivirus programs. They would be installed on the users computer without the users permission and nearly cripple the computer from functioning. Strong wording would be used such as a keylogger installed that is tracking all the keys entered into the computer or that the persons bank account can now be accessed remotely. There were hundreds of these fake antivirus programs going around a few years back but most of the holes have been patched security wise from Microsoft and thankfully government agencies around the world have cracked down on those making these fake virus programs and those who where marketing them.

Safe Browsing Habits

There is no full proof system out there to product yourself from getting infected with a virus.

The first recommendation is to have an active antivirus client installed.

The next would be to avoid installing software from vendors you do not trust and only install software from trusted sources.

Avoid websites that spawn lot’s of ads. Porn sites are a lot cleaner than they used to be but they still can carry lot’s of malicious code.

Keep your plugging and extension updated and remove those you no longer use.

Keep your web browser updated and if you still use flash be sure to always have that updated and remove the old flash version.

When checking e-mail avoid opening attachments unless you fully trust the source and even then take caution as that persons e-mail account could of been hacked.

2 Step Authentication

Many e-mail services and social accounts as well as banks now allow for 2 Step authentication. This in it’s simplest terms means you need to have 2 pieces of information to gain access to the system.

Often times this will be your password as well as a security code found that is unique to you that rotates every minute. This is often stored on the end users phone.

While it may sound complicated they are simple programs to use and go a long ways in protecting your online accounts from hackers.

After you enable 2 Step authentication on your first login you are generally asked if you want them to remember your device. If you are on your home computer you can say yes and you won’t have to enter in the second code every time.

If you attempt to login on a different computer you will be challenged again with the second code and would need that to login.

Passwords

It’s a good idea to have separate passwords for every account you have online. This means your facebook account will not have the same password as your bank account or e-mail account.

It can be hard to keep track of dozens of different passwords which is why I recommend all users use a password management program like roboform or Lastpass.

Protecting Your Smart Phone

With smart phone use constantly on the rise more and more threats are being made for Smart Phones. Generally most users have little to worry about and by taking just a few extra measure you can protect you phone and privacy.

It’s a best practice to always have your phone locked when not in use. This will stop someone from gaining access to your mobile device and messing with your personal setting and information.

Only installing apps from trusted sources such as the App Store and Play Store.

Taking caution to remove apps no longer in use on your phone as well as monitoring your phone activity after installing and app. You may love a new game you just downloaded but if you start getting pop ups all the time when browsing the web normally there may be active code in that free app that is pushing advertising onto your phone. Those kinds of apps you should remove immediately