What is a Computer Virus

In its simplest form, a computer virus is basically some form of software with nefarious intentions which continuously duplicate itself much like a regular virus would do within a human. This program typically alters the behavior of some device as it continuously duplicates itself so as to make it harder to purge from the system. This is accomplished through exploits and vulnerabilities found within the software to aid the virus' creator; to gain unwanted access to the system or to perform unwanted actions on the system.

Types of Computer Viruses

There exists several types of viruses in this world to help these software writers do what they want. One of the most common ones is called a trojan and is taken directly from the Ancient Greek story involving a wooden horse of deception. Just like in the story of the wooden horse being a deceptive gift that was filled with soldiers, a trojan virus is a type of software that is presented to do one thing but in fact, performs a different action; usually nefarious. Another term for this type of virus is called malware

Spyware is another common type of virus which is basically a program on the machine to allow the nefarious actor and creator of the program to record information. This type of software can be things such as a screen recorder which records everything you do on the machine or a keylogger which can capture every key you type on the keyboard. These types of viruses are usually used strictly for information gathering for things such as bank credentials, social security numbers, and other such sensitive information.

Ransomware has been becoming more popular within the last few years and these types of viruses actually force the entire device or some feature of it into a locked down state. Once done, the virus writer will usually have a trigger that can restore the machine but only after the target meets their demands by paying a ransom

Countermeasures

One of the best ways to avoid these nefarious programs being installed on your machine is to consciously be aware of the websites you're browsing and downloading software from. If the website or software is from an untrusted source, you should not trust it and shouldn't download anything.

Failing that, antiviruses is a type of software which is used to help purge a device of these viruses. They are programs developed with the toolset to quarantine viruses to stop them from spreading and to eventually remove them from the system. To do this, they perform a series of scans on the device's files that cover everything within their scope as viruses can exist anywhere on a machine's software.

Make a good habit of backing up and saving an earlier image of your device's state. The reason for this is because a system restore can return a device's internal files to an earlier point in time; a point in time when the system's files weren't infected with a virus. What this does mean, however, is that you run the risk of losing some data and files that did not exist at that point in time either, so do note that.