Information Technology Reference
In-Depth Information
games. Today, however, bots are frequently used to support illegal activities. A collection
of bot-infected computers is called a
botnet
, and a person who controls a botnet is called
a
bot herder
. Botnets can range in size from a few thousand computers to over a million
computers. In most cases, people have no idea that their PCs have been compromised
and are part of a botnet.
It's been estimated that as much as 90 percent of spam is distributed through bot-
nets [40]. Bots can also be used as spyware, stealing files or logging keystrokes to gain
credit card numbers or other sensitive information. Botnets can also be used to support
distributed denial-of-service attacks, which we discuss in Section 7.4.3.
The sophistication of bots continues to increase. Computers typically have
signature-based detection schemes to identify and destroy bots by looking for partic-
ular patterns in their underlying machine code. To counter these detection schemes,
programmers are now creating bots that are able to spin off functionally equivalent bots
with somewhat different machine code.
Three defensive measures are important in protecting personal computers from mal-
ware: security patches, antimalware tools, and firewalls.
Some kinds of malware exploit vulnerabilities in software systems, and software
makers respond by modifying their code to remove the vulnerabilities. At regular in-
tervals software makers release security patches so that the users of the software can
update their systems to remove the vulnerabilities that have been uncovered. In fact,
most worms exploit vulnerabilities for which security patches have already been created.
That means they can only infect those computers that have not been kept up-to-date
with the latest patches.
Antimalware tools are designed to protect computers against malware, such as
viruses, worms, Trojan horses, adware, and spyware. Antimalware software can be used
to scan a computer's hard drive, detecting files that appear to contain viruses or spyware,
and deleting the files (with the user's approval). The rapid rate at which new malware
appears necessitates frequent updating of these tools.
A
firewall
is a software application installed on a single computer that can selectively
block network traffic to and from that computer. A firewall gives the user the ability to
control which programs running on the computer are able to access the Internet. One
weakness of firewalls is that they are vulnerable to being manipulated by malware. If a
computer is infected by a piece of malware, the malware may be able to shut down the
firewall, since it is running on the same computer.
The Internet plays a vital role in the economic life of developed nations. Its effects in-
clude streamlining interactions between manufacturers and their suppliers, stimulating
the creation of new companies, fostering the development of new business models, mak-
ing online videoconferencing much more affordable, and changing how people shop.
