Information Technology Reference
In-Depth Information
of worms range from destructive to annoying. A worm might delete files
or direct users to a fake website, or it might just do something annoying
like swapping left and right mouse button actions. At the very least, a
worm will consume network bandwidth.
Some worms are designed to compromise the user's email address book and send itself to all the user's
contacts. If you receive an odd or unexpected message from one of your contacts, it could indicate that
her address book has been infected by a worm. Before opening the email, contact the sender to determine
whether the email is legitimate and to alert her to the possibility that her machine has been infected.
CAUTION
Trojans
According to Greek mythology, the Greeks conquered the city of Troy
through trickery. They constructed a large wooden horse, which they
presented to the Trojans as a gift. Unbeknownst to the Trojans, however,
the Greeks had hidden a select team of soldiers inside the horse. After
the Trojans dragged the horse inside the city walls, the Greek soldiers
emerged from the horse and opened the city gates, enabling the rest of
the Greek army to swarm the town.
It is after this horse, called the Trojan horse, that Trojans are named. A
Trojan is a piece of software, such as a game or utility, that may look
innocent but has a malicious purpose. Typically, the user knowingly
installs the game or utility, but doesn't realize there's a Trojan inside.
When the user runs the program, the Trojan starts running in the back-
ground, often without the user's knowledge.
Trojan A piece of malicious software that looks
harmless but has a detrimental effect on a com-
puter when it runs.
A Trojan can do nasty things to a computer, but more likely it is there to
gather information. For example, many Trojan programs are keyloggers.
As described, a keylogger records all the keys the user presses on the
keyboard and saves them in a file. It then sends the file with the user's
keystrokes to the person or group who sent the Trojan. In this way,
whoever sent the Trojan can learn what the user does on the computer.
More importantly, they can uncover the user's username and password,
enabling them to log in themselves.
A common type of Trojan is one that displays a screen that recommends
that you purchase and download some type of anti-malware software, as
shown in Figure 11.3. In this case, however, the software is fake and will
probably put more Trojans on your computer. Worse, if you buy it, the
thieves will then have your credit card details.
Another type of Trojan runs spyware. Spyware is software that moni-
tors what the user does on the computer without her knowledge. It then
sends the information it gathers to a third party, which uses it to target
the user with pop-up advertisements—often for fake products.
spyware A type of malware that spies on the
user's activities and reports them back to the
spyware's developer.
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