The 4 Symptoms of a Computer Virus You Need to Know

What can viruses do? Let’s diagnose the key symptoms of this type of malware.


In our previous blog posts, we’ve talked about how to remove a virus from a computer, iPhone, or iPad. But how do you spot one in the first place? Clario is here to help you by answering the following questions:

Let’s start with the basics and first look at what defines a virus.

What is a computer virus?

As you may know, a biological virus is a tiny parasite relying on living cells for survival. Viruses live at the expense of the host, which can be an animal, plant, or bacteria. Harmless on their own, a virus starts reproducing as soon as it attaches to a host cell, invading other cells and causing disease.


A computer virus is very similar to its biological counterpart. It’s a piece of code designed to copy itself and make changes to a computer without a user’s permission. 


Computer viruses are on the increase. It's better to be safe than sorry. Clario is here to give you a worry-free digital experience. Combining protection software with built-in 24/7 support from live security experts, it makes sure your digital life is safe. Download Clario and keep your device malware free.


Unable to function without a host, this type of malware travels from computer to computer, program to program, file to file. The dependence on a host and its self-replication capabilities make a computer virus different from other types of malware.

Four stages of computer virus infection

The causes of computer viruses are similar to how we catch the flu – everything revolves around us, humans. But while the flu is spread by coughing and sneezing, computer viruses get into our devices when we unsuspectingly click on attachments of unknown origin or browse dubious websites.


And just like with the flu, you won’t immediately see the effects of a computer virus as the symptoms tend to emerge later on in the infection. In most cases, there are four stages of computer virus infection.



When a virus first infects a computer, it may remain ‘asleep’ for a while to avoid suspicion. Some viruses ‘wake up’ after an infected program has been opened a certain number of times, while other viruses wait until a certain date. Either way, you won’t notice anything wrong during the dormancy period.



After a virus ‘wakes up’, it starts reproducing itself, assembling the army to implement its mission. During the replication period, you wouldn’t usually notice any symptoms. However, the virus may be busy spreading itself to other computers by sending infected files to everyone in your contacts list. In this case, you may find your computer runs slower than usual.


3️⃣Trigger event

A trigger event gives the virus a signal to act, to start bringing the hacker’s intent to life. Depending on the virus type, anything can be a trigger, including a certain number of virus copies or a particular date.



This is the phase where the virus implements its mission, which can be anything from stealing your passwords to making it impossible to use the internet. Unfortunately, the main symptoms appear during this stage.

What viruses can do?

From being an annoyance to wrecking severe damage on your device, computer viruses can do many things to their ‘hosts’. It all depends on the hacker’s intentions, which may range from terrorism to the desire to just demonstrate their skills.


Viruses can delete programs, manipulate keyboards, give access to sensitive information, or flood a network with traffic, making it impossible to do anything online. Can a virus destroy your computer? Yes.


Nevertheless, in the majority of cases, a computer virus is usually no more than a nuisance, and a problem which is easy to fix. But in some cases, viruses can lead to much more serious consequences.


For example, the ILOVEYOU virus sent itself to 50 million users worldwide and added a password-stealing program to Internet Explorer, causing damage of up to $15 billion. And the Sobig.F virus stopped computer traffic in Washington DC, causing $37 billion in damages.


But are all computer viruses harmful? You may be pleasantly surprised to hear there is some sunshine among these dark clouds of evil intentions.


For example, the Cruncher virus saves you hard drive space by compressing every file it infects. The Linux.Wifatch virus functions as an antivirus program, though there are better ways to protect your computer. Still, ‘good’ viruses are only a small subset of all of them.

Effects of computer viruses

Сomputer viruses are wholly dependent on their hosts. Just like their biological twins, this type of malware doesn’t alert you after it has infected your computer. Rather, it tries to remain unnoticed for as long as possible. So, what does a computer virus look like in terms of symptoms? Below are the most common signs.


Slower operating speed

Running programs in the background slow down the computer’s speed. Since a virus is designed to perform specific actions on your computer, poorer performance is inevitable. So, if your computer takes ages to start or programs are taking longer than usual to open, you might have caught a virus.


Issues with programs and files

Are there missing files? Are you unable to open certain applications? Do unknown programs start when you turn on your computer? Or, have new files, folders, or applications appeared on your hard drive, ostensibly out of nowhere? If so, then chances are malware has taken over.


You see, similar to biological viruses, computer viruses are known for their ability to attach to files and applications as they exist at the expense of these hosts. So, it isn’t surprising to see the first symptoms of a virus when working with your files and applications.


The most common target of viruses is system files. Without them, a computer system might not function correctly or at all. Thus, by infecting these files, a hacker can target the entire system. Such modifications won't just cause problems for the system itself but can also help the hacker control your computer remotely.


Weird behavior

The effects of computer viruses are only limited by the hacker’s creativity. For example, after infecting the user’s computer, the Elk Cloner virus displayed a poem threatening to ‘stick to you like glue’. 


The Ika-Tako virus replaced all files, programs, and documents with pictures of cuddly squids. If your mouse pointer starts jumping around the screen, it most likely isn’t a poltergeist – it’s probably either a drop of water on your touchpad or a computer virus.


Other effects

Certainly, poor performance, issues with programs and files, and weird behavior are not the only symptoms of infection by computer viruses. For example, if people from your contacts list start receiving strange attachments from you, it’s probably the sign of a virus at work (don’t forget to immediately change your passwords and ask everyone NOT to open all those attachments). Or the fact a virus is busy self-reproducing via the web might lead to high network traffic (here's how you can check your network traffic).


The other warning signs of a virus include your browser home page redirecting you to an unfamiliar website, your hard drive space suddenly running out, your system freezing for no reason, or your battery draining much quicker than usual.


* * *


While in some cases you can just get over the flu, a computer virus leaves no alternatives – ‘vaccination’ is the only way to survive. How?


Take care of your digital wellbeing and let Clario take care about the rest. Our antivirus can ward off even the dangerous computer viruses, ensuring you're completely safe online.

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