What's Virus
BOh no! I haven't saved it to the USB yet!
AWhat happened? You are noisy!
BSpreadsheet software doesn't work!
AThat's too bad. Computer virus may have done it.
BWhat? Is that true? What should I do?
ALet's examine the computer virus!
BWaa! Ihave no time to do that!

What's virus

We must remember the computer virus when we use the Internet.
Do you know that "the computer virus"means many kinds of software?
There are three conditions, and computer viruses meet one or more of them.


(1)Self contagious function

Computer viruses replicate themselves and invade other computers.
We call this function "Self contagious function".
If a computer infect the computer virus, computers around it is influenced by it.
Some of viruses don't have this Function. We call them "Trojan Horse".
It is explained atTrojan horseで説明しています。

(2)Hiding function

Computer viruses need some time to start raging.
It is like a time bomb.
So it is sometimes difficult to guess why the computer infect the computer virus.
Of course, some of computer viruses don't have this function.

(3)Onset function

Computer viruses destroy important files and personal informations.
Some of computer viruses have diffusion function.
They publish personal imformation on the Internet.
They are scary viruses.

Who Made Definition?

By the way, who made definition?
It is made by Information-technology Promotion Agency.
The definition is enacted in 1995 and revised in 2000.
They always collect virus information and research security.
If you are interested in IPA, click Here.

The Law About Virus

Japanese Nation enacted the law about anti-virus.
If you make something that make other computers move arbitrarily,it means you break the law.
But number of virus is increasing.

Trojan Horse

Do you know the word "Trojan Horse"?
It was used in the Trojan War.
This virus doesn't self contagious function.
In recent years, new computer viruses like Trojan Horse is made.


Trojan horse has many way to invade the computer.
Sent by e-mail,feign anti-virus software...
They don't start in automatic.
So one of countermeasure is "Don't open suspicious files".
But some computer can't display extensions, and user open trojan horse.

How to attack

Trojan horse uses two files.
They are "Server" and "Client".
Server invende the computer, and remodel Firewall, it is a function that is important function about security.
Then, it make anti-virus software invalid not to delete itself.
After server's preparation, client invende the computer and steal personal information.

Damage case

Trojan horse steal money and password when we use Internet banking.
Trojan horse can avoid fraud detection system so user can't notice that it invended.


We will introduce contermeasures against trojan horse.

(1)Don't open untrustworthy files!

In recent years, computer warns when user open suspicious files.

(2)Update security at any time!

Viruses and anti-virus softwares are steady progress.

(3)Introduce anti-virus software!

Anti-virus makes computer security more strongly.
BOh! Did I forget to update anti-virus software?
ACheck it!
BI updated it three hours ago...
ALook at this!
AUSB you saved the text is missing!
BAAAAHHHH! I must rewrite it again!!!!