What is a 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 become 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?
Perhaps 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 example, before you put a disk into your computer's drive (should you have one) make sure you know that the person you received it from has an uninfected computer.
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.
Visit the Where can I get anti-virus software? section below if your computer has no anti-virus software installed. Once installed, let the software check your computer for virus infection. You may be surprised at what it finds. Make sure that the anti-virus software is always loaded when you start your computer so that it can check any floppy disks that are inserted, etc. As new viruses are constantly being released you will need to make sure your computer regularly downloads the latest virus definitions file from the software maker's Web site.
Asahi Net's Security pages offer suggestions for protecting your computer, including updating it's operating system.
Asahi Net's Virus Check Service is also available. For a small monthly charge member's can have their mailbox(es) checked for viruses before their mail is downloaded to their computer.
My computer is infected-what can I do?
If you are sure your computer is infected and you haven't been led on by an email hoax (see below), run your anti-virus software and let it repair any infection, if it can. If your problem is worse, for example you find that you cannot start you computer any more, you may need professional help - so contact the maker of your computer and ask them what to do. They may have to instruct you how to re-install your operating system.
If you have no anti-virus software, visit the Where can I get anti-virus software? section below to download the software, or buy some at a computer store.
You may also want to contact the person you received the disk, email, etc. from and ask them if their computer is infected.
Note about hoaxes. Unfortunately there are people out there that originate hoax email telling others that their computer is either infected or will be infected by a virus. Naturally the receivers of such hoax email are alarmed and may follow the hoaxer's instructions to 'please pass this on.' If you are wondering whether the email you received is a hoax or not, take a look on the following pages to see if the title of your email is listed.
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.