[Tip 1]
What is Computer Virus? Points to countermeasure.

What is Computer Virus?

A virus is typically a piece of computer program that has been written to cause some inconvenience to a computer user or even cause damage to data on the computer or damage to the way the computer operates.

Once the virus has entered your computer it inserts itself into other programs that are running on the computer, such as the key programs that run to operate your computer, or the program you use to send and receive email.
Therefore, when these programs are run, the virus program is also run, with undesirable results.

For example, a virus which has infected your email program may also attach itself (invisibly to you) to any email you send to other people. In another example, a virus may lie dormant in your operating system until a certain day of the year has been reached, and then run, deleting files from your hard disk drive.

Four types of virus are:

- Memory-resident viruses -
These viruses hide inside the computer's memory (RAM) and are activated when the computer is turned on, infecting opened files.
- Macro viruses -
Maybe the most common type of virus, it infects applications like Microsoft Word or Microsoft Excel which use macro languages.
- File infectors -
These viruses attach themselves to program files, usually certain .COM or .EXE files. When the program file is run, the virus program inside them is also run.
- Boot sector viruses -
These viruses attach to the DOS boot sector on diskettes or the master boot record on hard disks. The find their way onto your computer from floppy disks containing the boot disk virus. The floppy disk is inserted into the computer and the virus writes itself to the master boot record of the hard disk. When the computer is restarted, the master boot record is read, and the virus is loaded into your computer's memory.

In what ways can my computer be infected?

Any time that data is received into your computer, it is susceptible to becoming infected. This includes receiving disks or USB clips/storage devices from friends who may have copied files onto them for you, without knowing that their computer is infected and that the files they are copying are also infected.

When connecting to the Internet and viewing Web pages or receiving email you also increase the possibility of receiving a virus, such as in an email attachment, the virus being run when the attachment is opened.

How can I protect my computer from infection?

The best way of protecting your computer from infection is to be aware of how the computer can be infected and make sure that you know where the data you are receiving into your computer comes from.

For those sending and receiving email, be particularly careful of email you receive containing attachments. If you haven't expected to receive an attachment from the sender,DO NOT OPEN THE ATTACHMENT, even if the sender is a relative or close friend begging you to open it.

Where can I get anti-virus software?

Here is a short list of just some of the makers of anti-virus software, there are others.
Click on the links to be taken to their homepages from which you will be able to download the software.
Please note that we advise you to read carefully the instructions on the maker's homepage before downloading, such as the size of the file to download and how long you may have to be on-line to download it.
In particular, please make sure that your computer system is capable of running the software.
Note that anti-virus software is generally not free - you usually have to pay for it.

Other Asahi Net's Security pages offer suggestions for protecting your computer, including updating operating system.

Check Your Security Status

Asahi Net Email Virus Check Service is also available. With only a small monthly charge, member's can have their mailbox(es) checked for viruses before their mail is downloaded to their computer.

Computer viruses are evolving.

Recently, new types are emerging and they can sneak in such mentioned countermeasures. These derivative viruses can invade into your computer just by browsing a malicious homepage, which automatically download malicious files. To prevent this, you must have the most updated anti-virus software installed into your computers.