Just as malware is written to exploit vulnerabilities in computer
systems, the distribution of malware exploits the stupidity of users.
Malware is typically spread in the following ways:
Email attachments
One of the most common ways viruses make their way into computers
is through spam. Attachments are embedded in these junk email messages
and sent by the millions to every email address in existence, for
unsuspecting recipients to click, open, and execute. But how can people
be that dumb, you may ask? Well, consider the filename of a typical
Trojan horse:
kittens playing with yarn.jpg .scr
Since Windows has its filename extensions hidden by default (see
Chapter 2), this is how the file looks to most Vista users:
kittens playing with yarn.jpg
In other words, most people wouldn??™t recognize that this is an .scr
(screensaver) file and not a photo of kittens. (The long space in the filename
ensures that it won??™t be easy to spot, even if extensions are visible.)
Crashes and Error Messages | 279
Troubleshooting
And since many spam filters and antivirus programs block .exe files,
but not .scr files??”which just happen to be renamed .exe files??”this
innocuous-looking file is more than likely to spawn a nasty virus on
someone??™s computer with nothing more than an innocent double-click.
So, how do you protect yourself from these? First, don??™t open email
attachments you weren??™t expecting, and manually scan everything else
with an up-to-date virus scanner (discussed later in this section).
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