Does reformatting the computer destroy all viruses and trojans that were on it?

Answer 1

Everybody who answered "yes" has no clue what they are talking about. OK, let's try a real answer.

Generally, the answer is "no". However, most of the time it will do a reasonably good job. It all depends on where the virus is and how the formatting is performed.

First of all, you must understand that there are two very different kinds of formatting - high-level and low-level formatting. Low-level formatting is performed when you want to prepare a disk that just came from the factory to be ready for writing. It does such things like creating sector markers and checksums. It is a destructive operation - once it is performed, the data from the disk cannot be recovered with conventional mean. (Parts of it can still be recovered using special equipment, generally not available to the public.) It is also an operation performed on the whole disk. It is unlikely that you've ever had to low-level format your disk; nowadays most disks are shipped already formatted. Depending on the hardware of the disk, different methods are used to low-level format it; see the sources for a site that lists low-level formatting utilities for various disk manifacturers.

High-level formatting is performed not on the whole disk but on a particular partition. Partitions are created with the utility FDISK (comes with DOS and Windows). Each partition can contain a disk volume or operating system. High-level formatting is what you do when you want to install an operating system (e.g., Windows) on an empty but already low-level formatted hard disk. Each operating system requires a different high-level formatting procedure. That is, you cannot use the DOS/Windows high-level formatting utility FORMAT to format a disk, on which you plan to install Linux; instead, you should use a Linux disk formatting utility.

High-level formatting is *not* destructive. That is, it doesn't "wipe out" your data. Instead, it wipes out only the area on a disk partition that says where the data is. Since the operating system uses this area to locate the data, it *looks* as if the formatted disk is empty - but the data is still there and there are many utilities that can recover it. Think of this area as the table of contents of a book. If you destroy it, you'll have trouble locating a particular chapter, even though the chapter is still there.

When you say "formatting", you're most likely thinking about high-level formatting. If the virus is in a file on your disk, high-level formatting will not destroy it - but it will make it inaccessible to the operating system, which in most cases is good enough, since it won't be able to run.

However, viruses can reside not just in files. Each disk partition (e.g., a logical disk volume like C:) has a special sector at the beginning, called a boot sector. It contains a small program that locates the files of the operating system and loads them at boot time, if the partition is bootable. There are viruses which reside in the boot sectors. A high-level format will destroy them, since it writes a fresh boot sector.

Each disk that contains one or more partitions has also a specail sector at the very beginning, called a master boot sector. It contains the partition table that says where each partition begins as how large it is, and also a small program, which locates the bootable partition and loads its boot sector at boot time. There are viruses which reside in the master boot sector. A high-level format will *not* destroy them, since it does not touch the master boot sector. However, you can use the DOS/Windows program FDISK with the command-line option /MBR to make it write a fresh clean copy of the master boot sector - this will destroy any virus hiding there.

Note, however, that most boot and master boot sector viruses have problems working under the contemporary operating systems like Windows or Linux (although they were the most common type of viruses under DOS), so it is unlikely that your computer is infected with one of them. Still, to be on the safe side, use an up-to-date anti-virus program to check.

Finally, remember that all these operations are safe to perform *ONLY* if the virus is not currently running. If it is running, it can detect your attempts to overwrite it can can re-direct them, so that in fact you overwrite something else and the virus remains intact. That's why it is recommended that you boot from a known-clean disk (e.g., a CD-ROM) before trying to fight viruses.

Personally, I would recommend *against* you trying to get rid of a virus by formatting your disk. This is not something an unexperienced person should attempt. Most likely, you will just lose your data and might even fail to get rid of the virus. Also, it is *always* possible to get rid of a virus without formatting your disk in any way.

My recommendation is that you use an anti-virus program that knows how to remove the virus that you have.

Answer 2

Yes. It wipes everything clean.

Of course you do know you have to reinstall all your drivers. Its just like getting your computer for the first time (Nothing on it)

its a good idea if you have viruses and trojans.

Answer 3

In most cases yes.

There are some very rare viruses that can corrupt your BIOS and in that case, you will need to get a new BIOS chip on your motherboard or a new motherboard entirely. The chances of this happening aren't likely though.

Answer 4

First I recommend you use a program that wipes all information off your hard drive. Then proceed to format the hard drive. This will wipe out any viruses or malware on the PC.

Answer 5

Yes, but be aware of any data you may have saved. You may reload any viruses or trojans that may be hiding in your saved data! Install an antivirus software before reloading any data.
(When I say saved data, I mean anything you may have saved onto disc.)

Answer 6

reformatting wipes out everything

Answer 7

Yes, it will. I'd love to say more that would make you pick me as the best answer, but the answer is simply yes.

Answer 8

Yes ... U need to do full format