What Are The Different Types Of Computer Viruses?

A computer virus is a software program designed to replicate itself and spread from one computer to another without the user's knowledge or consent. It can infect computers by attaching itself to legitimate programs or documents, spreading through email attachments or file-sharing networks, or exploiting vulnerabilities in computer operating systems or other software. Computer viruses can cause a variety of problems, including slowing down or crashing computers, stealing personal information, corrupting files and data, or even rendering computers unusable. Anti-virus software and safe online practices can help protect computers from viruses and other malicious software.
Types of Computer Viruses
Every computer virus has a payload that performs an action. The threat actor can code any malicious activity into the virus payload, including simple, innocuous pranks that don’t do any harm. While a few viruses have harmless payloads, most of them cause damage to the system and its data. There are nine main virus types, some of which could be packaged with other malware to increase the chance of infection and damage. The nine major categories for viruses on computers are:
Boot Sector Virus
Your computer drive has a sector solely responsible for pointing to the operating system so that it can boot into the interface. A boot sector virus damages or controls the boot sector on the drive, rendering the machine unusable. Attackers will usually spread this computer virus type using a malicious USB device. The virus is activated when users plug in the USB device and boot their machine.
Web Scripting Virus
Most browsers have defences against malicious web scripts, but older, unsupported browsers have vulnerabilities that allow an attacker to run code on the local device.
Browser Hijacker
A computer virus that can change the settings on your browser will hijack browser favourites, the home page URL, your search preferences and redirect you to a malicious site. The site could be a phishing site or an adware page used to steal data or make money for the attacker.
Resident Virus
A virus that can access computer memory and sit dormant until a payload is delivered is considered a resident virus. This malware may stay dormant until a specific date, time, or a user performs an action.
Direct Action Virus
When a user executes a seemingly harmless file attached with malicious code, direct action viruses deliver a payload immediately. These computer viruses can also remain dormant until a specific action is taken or a timeframe passes.
Polymorphic Virus
Malware authors can use polymorphic code to change the program’s footprint to avoid detection. Polymorphic viruses make it more difficult for an antivirus to detect and remove them.
File Infector Virus
To persist on a system, a threat actor uses file infector viruses to inject malicious code into critical files that run the operating system or important programs. When the system boots or the program runs, the computer virus is activated.
Multipartite Virus
These malicious programs spread across a network or other systems by copying themselves or injecting code into critical computer resources.
Macro Virus
Microsoft Office files can run macros, and these macros can be used to download additional malware or run malicious code. Macro viruses deliver a payload when the file is opened, and the macro runs.
What Causes Computer Viruses?
Computer viruses are standard programs; only instead of offering useful resources, these programs can damage your device. For a threat actor to execute a virus on your machine, you must initiate execution. In some cases, an attacker can execute malicious code through your browser or remotely from another network computer. Modern browsers have defenses against local machine code execution, but third-party software installed on the browser could have vulnerabilities that allow viruses to run locally.
What Is a Computer Worm?
A computer worm is malware, just like a virus, but a worm takes a copy of itself and propagates it to other users. Worms can also deliver a payload and exhaust resources. For example, an email worm sends a copy of itself to everyone on an infected user’s email contact list. When it reaches recipient inboxes, anyone who runs the worm sends it to their contact list. Email worms exhaust storage space and spread very quickly across the internet, so they create issues differently than a computer virus.
What Does a Computer Virus Do?
The way a computer virus acts depends on how it’s coded. It could be something as simple as a prank that doesn’t cause any damage, or it could be sophisticated, leading to criminal activity and fraud. Many viruses only affect a local device, but others spread across a network environment to find other vulnerable hosts.