What is the FAT Virus?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 15 October 2019
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A FAT virus is a computer virus which attacks the file allocation table (FAT), a system used in Microsoft products and some other types of computer systems to access the information stored on a computer. The FAT acts like an index, keeping information about where on the hard drive materials are stored, which sectors of the hard drive are empty, and so forth. By attacking the file allocation table, a virus can cause very serious damage to a computer.

FAT viruses can work in a variety of ways. Some are designed to embed themselves into files, so that when the FAT accesses the file, the virus is triggered. Others may attack the FAT directly. Many are designed to overwrite files or directories, and material on a computer can become permanently lost. If a FAT virus is powerful enough, it can render a computer unusable in addition to destroying data, forcing a user to reformat.

Essentially, a FAT virus destroys the index, making it impossible for a computer to locate files, and the virus can spread to files when the FAT attempts to access them, causing corruption to eventually penetrate the entire computer. FAT viruses often manifest in the form of corrupted files, with users noting that files are missing or inaccessible. The FAT architecture itself can also be changed; for example, a computer which should be using the FAT32 protocol might abruptly say that it's using FAT12.


There are a number of ways to avoid infection with a FAT virus. Computer users should get in the habit of using robust antivirus software which is updated regularly, and they should scan their computers on a regular basis for any signs of viruses. It is also a good idea to avoid downloading material which does not come from trusted sources, to avoid websites identified as “attack sites” by browsers and search engines, and to use caution when connecting external devices to a computer. A friend's digital camera, for example, might carry a FAT virus which will be transferred along with the images on the camera.

If a FAT virus has been allowed to persist, it may be necessary to hire a computer professional to repair the damage and salvage the system. Removal tools are also available, with many antivirus programs providing removal as part of their suite of services. If a program does not have a removal tool, their website may provide references for removal tools, and operating system websites sometimes also host removal tools for common viruses.


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Post 2

@KaBoom - I'm sorry you lost some of your data. You should always have a backup though! Always! You never know what might happen to your computer system.

That being said, I had a lot of trouble with a FAT virus once myself. I had my data backed up, but I wasn't being very vigilant about scanning my computer for viruses on a regular basis. My computer came down with a bad case of the FAT virus, and it was pretty far along by the time I caught it.

I ended up having to reformat my whole computer. It was a pain, but it did take care of the problem.

Post 1

This virus has kind of a funny name, but it's definitely not a joke. I had a computer get infected with a FAT virus awhile ago, and I lost a lot of data.

Unfortunately, I didn't have all of the data backed up, so most of it was permanently lost. I learned my lesson though. I'm a lot more careful with what devices I hook up to my computer now, and I run a virus scan at least once a week.

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