Internet Firewall: Security Threats
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In our first article, we mentioned that while firewalls can shield a single computer or a network from a slew of threats, there are intruders that cannot simply be thwarted by firewalls. Here we discuss both kinds of threats.
The primary defense against most kinds of threats, such as malware and hackers, are firewalls. Malware is malicious computer code that includes viruses, worms, adware, spyware, and Trojan horses.
Virus
A computer virus is a term that has struck fear into the hearts of people since the first virus attacks decades ago. This form of malware infects files on your computer; when these files are run, the virus is given the chance to infect other files and relentlessly invade the computer. Viruses are programmed to do a variety of things, ranging from utter file destruction to simple "electronic graffiti".
Worm
Worms are similar to viruses, but they have two traits that differentiate them from their cousins. First, they install their own files rather than infecting others. Second, they spread like a disease over a computer network rather than within a single computer. Worms can be used to install other dastardly forms of malware, such as Trojans, adware, and spyware.
Adware
Adware seems relatively harmless at first sight - it's a program that displays advertisements while you're using it. After all, most adware are freeware, and the ads are just a way with which the freeware's publishers can recoup their development expenditures, right? Wrong. Adware is infamous because it sneaks spyware with it, and spyware is always bad!
Spyware
Speaking of spyware, these programs spy on you (hence the name) while you're using your computer. This form of malware is the most common one after viruses, and they do their damage just by invading your privacy - they collect information from your files and record your online activities and send them to a third party.
Trojan horse
Trojan horses, like spyware, spy on or otherwise steal information from you. Trojan horses are used by their creators to control your computer from their location. One of the webmasters of this site has experienced the fury of Trojans - back in his high school days (when he was new to the Internet and quite naïve), his dial-up Internet connection password got pilfered by a Trojan horse and sent to an online message board. End result: a titanic bill from the ISP a few days later. Fortunately, he didn’t have to pay for it!
Other threats
There are security threats that can't be dealt with by firewalls. One example is a denial of service attack, wherein an intruder sends hundreds to thousands of connection requests that overwhelm a network or a website. Here, the goal is to shut down the target rather than sneak into the system to do damage or steal information.
A variant of the denial of
service attack is the distributed denial of service
attack, which is even worse as it launches a lot, lot more connection
requests to swamp the target.
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