Computing for the Bewildered. By Bill Hayles

Hello again.

One topic seems to dominate my postbox month after month. The topic is
that of Computer Viruses.

I'm sure that the real damage these beasties cause is far outweighed
many, many times by the worry and anxiety suffered by those who wonder
if they have one when they don't, what it will do, and what they can do about it.

If you use any other computer than a PC running Windows, then you are
fairly safe.  Not because viruses aimed at MacOS or Linux systems can't
be written, but because virus writers aren't bothering, concentrating
instead on the widest "market" - the Windows based PC.

WHAT IS A COMPUTER VIRUS?
A computer virus is simply a piece of code - a
program - which finds its way onto your computer uninvited, usually by
pretending to be something else.  It will have a "payload", in other
words, it will be written to make your computer behave in an unwanted
manner.  The payload may be merely a nuisance, such as a message
appearing on your screen periodically, or, at the opposite extreme, it
can wipe all the data off your hard disk or, (even worse in my opinion),
transfer it to another unknown computer. That's what a virus CAN do. 
What it CAN'T do is to physically damage your computer, or you.

HOW DO I "CATCH" ONE?
A virus can only find its way onto your computer from an external
(computing) source.  A computer that is never connected to the Internet,
nor ever reads a floppy disk or CD-ROM cannot get a virus. Nor is it of
much use. Until a couple of years ago, viruses mainly spread through
floppy disks - a friend might "lend" you a piece of software.  His
computer had a virus, and yours was infected through the floppy. The
more "dodgy" the software, the more likely an infection. Infection
through commercially sold software is not unknown, although it is very
rare.
Today, the vast majority of viruses arrive on your computer uninvited
through the Internet.  There are different types of virus, such as
worms and trojans, but they all have one thing in common.  They come in
through your Internet link. There are three main ways.

(1) Directly, through an undetected connection.  All the time you are
connected to the Internet, the Internet is also connected to you, and,
unless you take precautions, anybody who wishes to can hack into your
system and upload a virus program onto it.  Fortunately, since most
people don't have a permanent connection, this method is very hit and
miss for the hacker, and is thus comparatively rare. If you have an
always-on connection, such as the increasingly popular ADSL, the
likelihood of one of these attacks increases, and you would be wise to
take precautions in the form of a firewall.  I hope to talk about ADSL
in a future article, and I will explain firewalls then.

(2) In a piece of software.  This is the same as using an infected
floppy.  You go to a so-called "warez" site, where software that would
otherwise cost you a considerable sum is available for free.
Unfortunately, as well as the required software, there may be uninvited
guests. Use such sites at your own risk.

(3) IN AN E-MAIL ATTACHMENT. This is nowadays the most common sort of
virus, and the one that causes the most worry. The e-mail may well be
from somebody you know.  Unfortunately they have a virus, and one of
the things it does is to attach itself to every e-mail they send (or
even sends itself, using your friend's Address Book) hoping you'll open
it because you trust your friend. So, some golden rules: (1) Only send
e-mails using plain text, not HTML. Although HTML code is in itself not
usually the source of a virus, it can trigger the execution of
attachments which MAY contain the virus. (2) Never open any attachment
without checking it first (more below). Therefore, disable any
"automatically open attachments" option, especially if you are using
HTML despite (1) above Even if an attachment IS a virus, it will do no
harm if it is deleted without ever being executed (opened) (3) Never
assume that a message from someone you know is "safe".

HOW CAN I PROTECT AGAINST VIRUSES?
It is impossible to guarantee you will never be sent a virus.  If you
want such a service, a few ISPs will check all incoming e-mails for you,
and remove any that appear to contain a virus.  Some of us have
misgivings about this censorship of traffic, but the companies are
quite open in what they do, and you may be one of those who find such a
service reassuring.
To a very considerable extent, you can help yourself, by understanding
what file extensions are, and to be able to recognise the ones that
might be dangerous. In a misguided attempt to make things simple, in
its default settings, Windows hides these extensions from you, the user.
So the first thing we must do is to reveal them.  Double-click on the
"My Computer" icon on your desktop, then select "Tools" from the menu
and "Folder Options from the drop-down menu. Now select the "View" tab.
You will see a list of options, some of which have a tick in the box
next to them ("checked") and others won't ("unchecked"). The option "Do
not show hidden files and folders" should be unchecked, and "Show
hidden folders and files" checked. By far the most important change is
to change the option for "Hide extensions for known file types" from
checked to unchecked - you want to see them!! Having made these changes,
you will be able to see the extension of any file attachment to any
e-mail.  The file extension is (usually) a three character code
following a full stop, which defines what sort of a file it is.  For
example, a file named pussy.jpg, whilst it may not be a picture of a
fluffy cat, is most definitely a picture file and, as such, cannot
contain a virus.  However, a file named pussy.exe is an executable file,
i.e. it contains code to be run, or executed, by Windows, and could
possibly contain a virus.
There is no need to understand what all the various extensions mean; it
is sufficient to recognise the dangerous ones.  The main ones to be
wary of are .exe, .com, .bat, .cmd, .pif, .reg, .lnk, .vbs, .scr, .chm,
and .js. Never, ever open a file with one of these extensions if you
receive one in an attachment.  Either delete it straight away, or, if
you think it may be genuine, e-mail the sender for confirmation.  Also,
you should be aware that a Microsoft Word or Excel document, .doc or
.xls can also contain malicious code, a so-called "macro virus", and
you should be wary of these if they are not from a trusted source. All
this is in addition to the main way to protect yourself, to use a virus
checker.  A virus checker checks software already on your computer,
looking for suspicious "fingerprints" which reveal rogue programs, as
well as hovering in the background checking anything you download..
Arguments rage as to which are the best virus checking programs.  These
arguments are mainly academic.  All anti-virus software works well if
kept up to date.  Even the greatest is worse than useless if it is not
periodically updated, ideally every month but at least every three
months.  I say worse than useless as if you have no protection software
then you are at least aware that you are vulnerable.  If you have out
of date software, you may be lulled into a false sense of security,
thinking you are protected when you're not.

WHAT IF I THINK I'VE GOT ONE? As Corporal Jones said, don't panic! Most
scares are nothing more than that - scares.  If your computer crashes,
it is most unlikely that a virus is the cause. If you can, scan your
system with up-to-date anti-virus software. If you can't, download one
from the Internet.  Don't worry about infecting "The Internet" - you
won't. The anti-virus software I use on my computers is ESafe Desktop,
and you can download a trial version from http://www.esafe.com.  If
you're really worried, e-mail me - but nobody else, as you may pass on
any infection.  My system is fortress guarded against viruses.  If your
e-mail contains a virus, then at least I know what I'm dealing with! If
I can help, I will. I give priority to pleas for help with virus
problems when it comes to allocating my time.

That's it for now, but if you have a question you'd like me to answer
in the column, please e-mail it to questions@billnot.com. However, I
can't promise to answer all queries personally.

If you have been, thanks for reading this.