The basic difference between a Trojan and worm is in their functionality. Trojan horse is: An imposter that claims to be something affordable but actually is malicious. The main difference between virus and Trojan horse is that the former can’t replicate itself. Trojan virus comprises of malicious codes that when it is triggered it often result in theft or loss of data. Trojan horse spreads only when one invites this program onto a system. It can spread instantly if you download running files from internet or open email attachment.

Worm on the other hand is: A kind of program that can easily replicate itself easily from one system to another without any aid of a host file. This is a sharp contrast to the feature of virus as it needs an infected swarm file to spread properly. Often worms exist within other files. Usually worm discharge document that already has worm macro inside it.

How Trojan And Worm Affects Your System:

Trojan horse and worm affect your system in individual ways. The virus Trojan has been named after the Greek soldiers who used to hide themselves in wooden horses to cause harm to the soldiers in opposition. Likewise, the virus also damages your documents and files without any notification. However, there are few Trojan viruses that don’t cause any such harm to a system, but most of them leave negative impacts.

• A few Trojan viruses are potential enough to monitor entire inter-connection of the system and can easily take in grip all passwords and e-mail addresses. Often the e-mails will be interrupted or sometime you will notice credit card detail have been copied, if Trojan attacks your system.
• This virus can be so affective that it allows a person in remote area to access your hard drive and find out all interesting document. This virus keeps the door open for other to install something worse in the system.

Worms:

Though worms don’t harm in a hidden manner, however they are more harmful than the Trojan viruses. As this virus can replicate itself easily, it often affects:

• Network environment in offices and disturb the workflow of the web hosts and   internet providers.
• Worms get embedded in different files like MS word. Once this document is read the worm gets discharged and travel freely from one network to another, carrying the contaminated documents with it.
• It is quite hard to detect the symptoms of Trojan attack easily, but worms can be noticed and removed as well, without any major hiccups.

Other issues:

Once a system gets affected with Trojan virus, anybody can use it for different purposes like to attack a website, make use of different proxy servers to conceal attacks and to send spasm in huge number. Protection against Trojan is as similar as virus. Any up-dated antivirus application can keep this virus away for a long time.

Worms on the other hand can operate the network on its own to send their copies to different PCs with the help of a security hole. It can affect a huge number PCs without a user’s intervention and spread rapidly. Worms are actually a well known malware, though most users confuse it as virus.