Types of Computer Viruses
Every 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 are:
The Nine Major Categories of Viruses are:
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.
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.
These malicious programs spread across a network or other systems by copying themselves or injecting code into critical computer resources.
A virus that can change the settings on your browser will hijack browser favorites, 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.
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 virus is activated.
Web Scripting Virus
Most browsers have defenses against malicious web scripts, but older, unsupported browsers have vulnerabilities that allow an attacker to run code on the local device.
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.
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 virus type using a malicious USB device. The virus is activated when users plug in the USB device and boot their machine.
Direct Action Virus
When a user executes a seemingly harmless file attached with malicious code, direct action viruses deliver a payload immediately. These viruses can also remain dormant until a specific action is taken or a timeframe passes.