Computer viruses are nasty little programs that are designed to lay waste to your computer. Some destroy files stored on your PC, while some trigger different software to malfunction. More nefarious viruses steal your confidential information and some even go to an extent to rig a system’s power load and cause it to catch fire. Some nasty little things these viruses are! So, the more you know about viruses and how they work, the more prepared you will find yourself when they come knocking. And with that thought, here are 7 computer viruses you should know about.
‘Nasty’ is underrated when we talk about this virus family. When a polymorphic virus infects a computer, before it starts multiplying it creates copies of itself with every copy slightly different from one another. And because this virus is capable of creating such duplicates constantly, it can be difficult for antivirus programs to detect it.
A resident virus is different from a non-resident virus in the way it functions. A non-resident virus needs to be executed first, before it begins its infection. However, a resident virus can activate itself whenever the operating system loads. It is able to do this because it stores and hides within the memory of the infected computer, which is why it is difficult to get rid of such viruses.
First, let’s understand what is a boot sector – it is a section on a computer’s hard drive or an external storage media. This section contains information which is required to boot a computer. A boot sector virus infects part of this boot sector called the master boot record (MBR) and replaces legitimate information with its own infected version. The virus gets activated before the operating system loads and it may make the infected computer unbootable.
While other viruses attack one component of a computer at a time, a multipartite virus attacks two. This virus can infect both the boot sector and the system or program files at the same time. This triggers infections at multiple sections in the computer – just like multiple bombs detonating at various places at the same time. Because of this dual infection approach, the multipartite virus can re-infect the same system over and over again until all its components are completely eradicated.
True to its name, an overwriting virus destroys the file it infects. It does this by overwriting data in the system’s memory. The virus can be removed only by deleting the infected file. Often, cleaning an overwriting virus means losing the infected programs and reinstalling them.
It’s also known as a browser redirect virus and so because it’s sole purpose is to redirect you to websites without your consent. Once inside a computer, it modifies the settings of the web browser (including default search engine and home page) and takes a user to malicious websites (in most cases). A browser hijacker spreads through malicious email attachments, free downloads or when a user visits an infected website. This virus can install a spyware on the infected system and this may compromise the user’s private data (personal or financial information). It can also install other viruses such as ransomware that encrypts a system’s data and demands money (ransom) in exchange.
Let’s first understand what is macro. Macro is a set of commands that can be installed in programs like MS Word or Excel to trigger a specific function automatically. It is mostly used for automating common, repetitive tasks. A macro virus is a malicious program that is written in the same macro language and replaces/alters a pre-installed macro in a program like MS Word or Excel. And when such a document is opened, it causes a series of actions to begin automatically. These actions include infecting every other document on a user’s computer, causing irregularities in text documents, accessing email accounts, sending spam messages to people in the user’s address books, etc. A macro virus can affect Windows, Linux and even Mac.
What we have described here about these 5 computer viruses is just one tiny aspect of what they do. Details on how viruses and malware function might not be easily comprehended by everyday users. But the main message here is that such malicious programs can turn your digital devices against you. And the only way you can defeat them is by educating yourself on cybersecurity and using a multilayered security solution that can stand between these threats and your computer.
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This post has been updated as of 13.3.2017