What is a Computer Virus?

So, what is a computer virus? It's annoying, irritating and the people who create these should slapped, just like a mosquito. Oh, and I forgot the important part, it's good for nothing.

Now that that's out of the way, let's look at computer viruses in a bit more detail.

Just like humans unknowingly contract or are infected by a virus, so does your computer. When you are infected by a virus, you don't feel so good. In fact, you feel lousy. The same goes for your PC.

Ok, PC's don't feel, but they don't operate like they should. I think that's why the computer fraternity uses the term, computer virus.

But what is a computer virus?

It's a program or piece of code that can replicate itself from one system to another.I still don't really get why people write viruses, but these programs are there to do harm to your PC such as wiping the hard disk or extracting personal information from your hard disk or sending spam from your email account.

The most popular reason for a virus these days, is to send spam emails from your computer. After you have been infected by this virus, it goes about scanning you address book and then start to send lot's of spam emails to everybody in your address book.

Some of these mails will have the virus as an attachment to the receiver. The receiver of this mail will see that you send this mail, and because he knows who you are, will open the attachment thinking it's save.

The virus will then infect this persons PC and start to scan his address book and send out mails to all in his address book and so on and so on. Can you see where I'm getting to.

This is a classic example of how computer viruses can spread. The programmers of these viruses are not stupid. They have found clever ways to disguise these programs. You do get antivirus software, but these programmers find ways to disguise their code in legitimate ways.

What is a computer virus? - Is email the only way for a virus to spread?

Unfortunately not. Using your email address book is but one way for a virus to spread. It's an easy way because people are suckers for clicking on attachments that they don't know from who it is. I did it myself at some stage, and I paid dearly.

Another way for a virus to spread is by replicating itself from disk to disk. These viruses will detect whether you have inserted a external device such as an USB flash drive or hard disk. It will then copy itself onto the external device.

When that person then inserts his USB drive in his computer, then the virus copies itself onto his computer and if that person then inserts his USB drive into another computer, then the virus copies itself onto that computer and so on and so on. You get the idea.

Another way for a virus to spread is via the network. These viruses spread to other systems using the local area network or LAN. This can be seen as a worm digging holes from one part of your garden to another.

These viruses can replicate using the companies active directory (AD) server. This is a server that holds all the information of users such as user name and password, email address and personal details. The program will "worm" itself through this user information and thereby infect other computers.

Again, I don't know why these people write viruses like this. It's just to annoy you.

What is a computer virus? - But how can a program on a hard disk do all this.

True, if a program just sits on a hard disk, it can't do much. You have to click on it or run it for it to start working. The thing is, these programs are resident in your computers memory. They usually run as background processes on your computer.

Another word for it is a, daemon program. When your computer starts up, it loads services in the background. It finds some space in memory and then does it's thing when needed. It's quicker than to load the program from hard disk every time it needs to execute.

You can see these "daemons" when you press "ctrl+alt+del" and select the task manager and "processes". Some of these viruses are quite clever. They actually run as legitimate programs. They have been written to occupy unused space or gaps in normal programs.

That's why it's so difficult to detect them. You can't just open the task manager and kill the process. It's embedded in a normal background process. It's been, infected.

What a computer virus? - How can I stop this infection?

These days, mail servers and mail clients will stop mails being sent out with attachments that are executable. They will scan your mail, and if there is a ".exe", ".com" or zipped attachment, prohibit you from sending the mail.

Viruses can also be embedded in a word document or excel spreadsheet by means of macros. When you open the document, the macro will run and the virus will do whatever it was programmed to do. That's why you will sometimes see your mail program warn you about a word or excel attachment.

Macro's are little pieces of code that automates a task in you document or spreadsheet. It executes, whatever instructions you give it, step by step. Perfect for virus programmers.

The best way to protect your PC is to use antivirus software. There are lot's of these programs available. Some you can try for free and then buy if you like it.

Some have a free version that you can use without the need to license. This only gives you basic protection. If you like it, you can then spend some bucks and get the full version.

Antivirus software also runs as a background process or "daemon" on your computer. It's job is to scan your memory for virus signatures. If it picks up a virus, it will warn you and ask if it could eliminate the virus. Sometimes it will immediately delete the virus, without asking.

These are usually known viruses.

What is a computer virus? - What can I do when I'm infected?

Like I said earlier, get a good antivirus program. These will scan your PC and delete all known viruses from your computer. This is no guarantee that your computer is clean.

Antivirus software also relies on a database of viruses. If these is a new one, they will create an antidote and update the database. Next time you run your scan, the antivirus software will download the database and kill the new infection.

They don't just rely on a database. They can also detect virus signatures of programs in memory, without the need to check a database.

What is a computer virus? - Should I reload my operating system?

If you have it bad, then sometimes it is a good idea to reformat your hard disk and reload. This is in extreme cases. If you have good antivirus software, then this would not be needed.

I'm a bit paranoid. When my antivirus continuously picks up infections, then I reload. If people continuously complain about viruses on my flash disk or external hard disk, I reload.

That's just me. It's a lot of work, but you don't have to do it. Just get a good antivirus program.

Some popular ones I use are, Norton antivirus, AVG and Kaspersky. They are well known and pretty good. Do some research on the subject. Like I said, there are many more excellent antivirus programs out there.

What is a computer virus? - Last words

I don't know who create these viruses or why they do. It might only be to annoy us or a teenager trying to impress his buddies. It might be criminals trying to get you personal or banking information.

Whatever the reason, keep clean. Invest in a good antivirus program and don't click on attachments if you don't know who they are from.

I hope you have a better understanding of what is a computer virus. It can be quite a complicated subject. I have tried to keep it simple but also give you as much information as possible.

You can do more research into what is a computer virus. The net is full of information, from basic to more advanced stuff.

What is a computer virus ? - Keep it clean.

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