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Essay: Understanding Computer Viruses, Trojan Horses, Worms and Other Malicious Software

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  • Published: 1 February 2018*
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A computer virus is type of malicious software program (malware) that, when it is executed, replicates by making file of its own replica (copying its own source code) or infecting other computer programs by modifying them. Infecting computer programs can include data files, or the "boot" sector of the hard drive. When this replication succeeds, the affected areas are said to be infected with a computer virus. The term virus is also commonly, but erroneously, used to refer to other types of malware. Malware includes computer viruses along with many other forms of malicious software, such as computer, Trojan, ransom ware, key loggers, spyware, rootkits, adware, malicious and other malicious software. The majority of active malware threats are Trojan horse programs or computer worms other than computer viruses. A Trojan horse is full of as much trickery as the mythological Trojan horse it was named after. The Trojan horse, at first glance will appear to be useful software but will actually do damage once installed or run on your computer.  Those on the receiving end of a Trojan horse are usually tricked into opening them because they appear to be receiving legitimate software or files from a legitimate source. When a Trojan is activated on your computer, the results can vary. Some Trojans are designed to be more annoying than malicious (like changing your desktop, adding silly active desktop icons) or they can cause serious damage by deleting files and destroying information on your system. Trojans are also known to create a backdoor on your computer that gives malicious users access to your system, possibly allowing confidential or personal information to be compromised. Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate.

According to law, malware is sometimes recognized as a computer contaminant, as in the legal codes of several USA. Spyware and other malware is sometimes identified embedded in programs supplied officially by companies ( downloadable from websites) that seems to be useful or attractive, but may have, for example, additional hidden tracking functionality that picks marketing statistics. Example of such software, which was described as illegitimate, is the Sony rootkit, a Trojan embedded in CDs sold by Sony, which silently installed and concealed itself on purchasers' computers with the intention of preventing illegal copying; it also reported on users' listening habits, and unintentionally created vulnerabilities that were exploited by unrelated malware. Software such as anti-virus, anti-malware, and firewalls are used to protect against any activity identified as malicious, and to recover from attacks.

A worm is similar to a virus by design and is considered to be a sub-class of a virus. Worms spread from computer to computer, but unlike a virus, it has the capability to travel without any human action. A worm takes advantage of file or information transport features on your system, which is what allows it to travel unaided.

The biggest danger with a worm is its capability to replicate itself on your system, so rather than your computer sending out a single worm, it could send out hundreds or thousands of copies of itself, creating a huge devastating effect. One example would be for a worm to send a copy of itself to everyone listed in your e-mail address book. Then, the worm replicates and sends itself out to everyone listed in each of the receiver's address book, and the manifest continues on down the line.

Trojan horse-

A destructive program that masquerades as a benign application. Unlike viruses, Trojan horses do not replicate themselves but they can be just as destructive. One of the most insidious types of Trojan horse is a program that claims to rid your computer of viruses but instead introduces viruses onto your computer.

The term comes from the Greek story of the Trojan War, in which the Greeks give a giant wooden horse to their foes, the Trojans, ostensibly as a peace offering. But after the Trojans drag the horse inside their city walls, Greek soldiers sneak out of the horse's hollow belly and open the city gates, allowing their compatriots to pour in and capture Troy.

Trojan horses are broken down in classification based on how they breach systems and the damage they cause. The seven main types of Trojan horses are-

1. Remote Access Trojans

2. Data Sending Trojans

3. Destructive Trojans

4. Proxy Trojans

5. FTP Trojans

6. security software disabler Trojans

7. denial-of-service attack (DoS) Trojans

Trojan horse software operates the same way, where Troy is your computer and the horse is the benign-seeming application. Trojan horses can assist an attacker into turning a user���s computer into a zombie computer, stealing various data such as credit card information, installing more malware, key logging and various other malicious activities. Also, it is possible for other crackers to control the compromised computer simply by searching for computers on a network using a port scanner and finding ones that have already been infected with a Trojan horse. Trojan horses continue to increase in popularity and currently account for the majority of known malware found on the web.


Some computer viruses are programmed to harm your computer by damaging programs, deleting files, or reformatting the hard drive. Others simply replicate themselves or flood a network with traffic, making it impossible to perform any internet activity. Even less harmful computer viruses can significantly disrupt your system���s performance, sapping computer memory and causing frequent computer crashes. An unprotected computer is like an open door for computer viruses. Firewalls monitor Internet traffic in and out of your computer and hide your PC from online scammers looking for easy targets. Products like Web root Internet Security Essentials and Web root Antivirus with Spy Sweeper provide complete protection from the two most dangerous threats on the Internet ��� spyware and computer viruses. They thwart threats before they can enter your PC, stand guard at every possible entrance of your computer and fend off any computer virus that tries to enter, even the most damaging and devious strains.

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