Difference Between Virus,Trojan horse and Worm

As all of you might have heard of Viruses, Worms and Trojan Horse . But do you know what are they? Some might confuse viruses with worm and trojan horses who had some knowledge about computer’s. You might have heard they can infect your computer system by infecting your system destroying your data. Yes they are similar in a way that they do the same damage. But they all are different in a way that they damage. But do you all know what is the difference between the three? I will give you some basic idea about them, their source and how they affect your computers. Knowing the differences can help you protect your computer system. 

VIRUS

Technically, a  Computer  virus is a malicious program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes as it can replicate(regenerate) itself and spread from one computer to another . You might have heard about viruses in human body. Computer viruses can make computer system sick but needs a host as a carrier just like virus in human body. Hosts may be a program or file. A computer virus attaches itself to a host (file, program or boot records of disks and diskette) enabling it to spread from one computer to another, leaving infections behind as it passes. In order to regenerate itself, a virus must be permitted to execute (open itself) code and write to memory. For this reason, many viruses attach themselves to executable (that can run) files that may be part of any programs. If any user attempts to launch an infected program or file (containing virus), the virus code may ran simultaneously.

But how does it spreads(replicate itself)? It can travel from one file to another on the same computer if the infected file is executed, from computer memory to a file on disk (here disk refers to an external drive such as pen drive, external HDD, DVD, etc.), on a disk that is carried from one computer to another, on e-mail attachment executable files, and over a modem or a network connection.

Now certainly one question arises over our mind at this point. What does it  infect and how does it harm computers?  The answer to this question is: Virus can easily corrupt the program it infects and you probably you have to reinstall the program in question. It may also cause you to reinstall your operating system if it remains longer after execution as it is capable of erasing data. A virus may be capable of damaging hardware like hard disk, DVD drive, processor, motherboard, etc. How can it damage hardware if it damages infected software (file, program, etc.)? Hardwares are controlled by softwares (operating system and drivers). Since it can replicate itself and is a piece of code(or software), it may somehow replace controlling software which will give it hardware control. Once virus is in position to control hardware, it can damage it.

TROJAN HORSE

 

Technically, Trojan horse is a malicious code hidden in an infected program such as a game or spreadsheet that looks safe but has hidden side effect. It may also be said that it works in disguise. When the infected program runs, it seems to be performing as user expects, but actually it is destroying, damaging or altering resources or information in the background. It is a self-independent program and  doesn't require any host to embed itself. It is often used to locate password or make system vulnerable to future entry or simply destroys data or programs installed on the Hard-Disk. A Trojan Horse is similar to Virus, except from the fact that it doesn't replicate itself. 

 

Trojan Horse history:  The most interesting part of name ‘Trojan horse’ is it’s history. After you read, you will be able to interpret why this code is named as ‘Trojan Horse’. Trojan comes from Greek mythology, which means people of Troy. In the mythology, the Greeks battled the Trojans. After years of being unable to break into fortified city, the Greeks built a wooden horse, filled it with soldiers and pretended to sail away. After the Trojans brought the horse into the city, the Greek soldiers crept out at night, opened the gates of Troy to the returning soldiers, and Troy was destroyed. In the same way Trojan Horse come into system without user’s knowledge and open’s it to most destroy the system.  

  

How does Trojan Horse spread?  The answer is that they generally spread through e-mail and exchange of disks and information between computers. They often sneak  inside free games, spreadsheet or some free utility.

 

How does Trojan horse damage?  Damage caused by Trojans are same as what virus causes. Most dangerous part of Trojan Horse's are that most of the time user's are unaware of the damage caused because of its Trojan's Horse masking effect( Which misleads user that the program is not infected). This is what makes it different from Virus. Moreover, it does not replicate as the Virus does. Trojan's stays in computer doing its damage and may allow someone from remote site to have complete control  and total access of your computer. Once unleashed, the Trojan often destructing computer's functionality,while allowing your computer to be used for notorious reasons. Trojan enable hackers to open backdoors within your computer system, giving them unlimited access to any files on your computer system and can even access any network you have installed. Some Trojans install a dialer, and utilizing your modem, you could discover your next phone bills landing over thousands of dollars in phone calls you never made. Trojans have been recently been developed where a surfer simply has to view an infected webpage, and a Trojan will auto-install immediately, without you doing anything other than simply viewing that page. An example of Trojan Horse would be a Christmas executable, pops up with an animated figure of Santa Claus and a Caption saying "Merry Christmas." In background, extra code could be deleting file or performing other malicious actions.

                                                         

                                          WORMS

 

A worm is a program designed to replicate without use of other program  or intervention or action by a user. It is self contained program that requires no host and run independently. It activates after creating process(needs a multitasking system) . The Worm can perform varieties of additional task as well, as is provided by the attacker. They are generally found on computers capable of Multi-Tasking and is connected to a network. Worms do not change the program although they may carry other infectious codes of Viruses and Trojan Horse.  

How worms spreads?  Worms are autonomous agents which is capable of propagating itself without use of another program or intervention or action by a user. It requires only multi-tasking system to replicate. They run independentely and travel from computer to other computer across network connections. Worms may have portions of themselves running on many different computers.

 

 Damage caused by Worms: Most worms disrupt services and create system management problems. Some worms scan for passwords and other loopholes and then send the information back to the attacker. If attacker gets information such as credit card info or any other sophisthicated things you can imagine what can happen. In some cases worms can install Trojan Horses or viruses that that cause damage to the systems.


Note: This is my first blog. So feel free to comment. Maybe there will be some errors surrounding Fonts but I will fix it afterwards.