Computer Viruses; come in many different many forms and can affect your machine in different ways. A virus can badly affect your computer by deleting files, replacing them or stealing your personal data.

Below are seven of the most common computer viruses you need to be worry about.

1. Boot Sector Virus

Boot Sector Viruses are some of the most dangerous viruses, because they infect the master boot record. They are very difficult to remove and often requiring a full system format. This is especially true if the virus has encrypted the boot sector or excessively damaged the code.

Boot Sector Virus mostly comes via remove-able disks, like USB stick. So it’s better not to open any USB on your PC until unless you are sure that it’s virus free.

2. Multipartite Virus

As it is evident from its name, a Multipirate Virus spreads in multiple ways, and it may take different actions on an infected computer depending on variables, such as the operating system installed or the existence of certain files.

They can simultaneously infect both the boot sector and executable files, allowing them to act quickly and spread rapidly.

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3. Polymorphic Virus

Polymorphic Viruses are one of the most difficult to detect for an anti-virus program and this is what makes them deadly. Anti-virus firms need to spend days or months creating the detection routines needed to catch a single polymorphic.

The reason polymorphic viruses are hard to detect it because they change their signature, binary pattern every time it replicates. If anti-virus catches one such virus, its replica becomes an entirely different piece of software, thus making it very hard for anti-virus to detect.

4. Direct Action Virus

Direct Action Virus is known as file infector viruses. The virus is considered “non-resident”; as it doesn’t install itself or remain hidden in your computer’s memory.

This virus works by attaching itself to a particular type of file – typically EXE or COM files. When someone executes the file, it springs into life, looking for other similar files in the directory for it to spread to.

On a positive note, the virus does not typically delete files nor hinder system’s performance. Aside from some files becoming inaccessible, it has a minimal impact on a user and can be easily removed with an anti-virus program.

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5. Resident Virus

Resident Viruses are the second type of file infectors. Unlike direct action viruses, they install themselves on a computer. It allows them to work even when the original source of the infection has been eradicated. As such, experts consider them to be more dangerous than the direct action viruses.

These viruses can be tricky to spot and even trickier to remove. You can split resident viruses into two areas; fast infectors and slow infectors. Fast infectors cause as much damage as quickly as possible and are thus easier to spot; slow infectors are harder to recognize because their symptoms develop slowly.

6. Overwrite Virus

Overwrite Viruses are one of the most frustrating viruses, even if they not particularly dangerous for the system as a whole.

That’s because it will delete the contents of any file which it infects; the only way to remove the virus is to delete the file, and consequently, lose its contents. It can infect both standalone files and entire pieces of software.

Overwrite viruses typically have low visibility and are spread via email, making them hard to identify for an average PC user.

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7. Spacefiller Virus

Spacefiller Viruses are also known as “Cavity Viruses”, and are the most intelligent than most of their counterparts. A typical way for a virus is to simply attach itself to a file, but spacefillers try to get into the empty space which can sometimes be found within the file itself.

This method allows it to infect a program without damaging the code or increasing its size, thus enabling it to bypass the need for the stealthy anti-detection techniques other viruses rely on.

Luckily, this type of virus is relatively rare, though the growth of Windows Portable Executable files is giving them a new lease of life.

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