Often people get confused about certain words that are quite commonly used in the field of computers. These include Trojans, worms and viruses. These are malicious software programs that can severely damage the contents inside a computer. However, all these three programs differ from each other. Knowing these differences can help a person in protecting his/her system in a better way.
Trojans -- These software programs have been named with reference to the wooden horse devised by Odysseus that contained Greek soldiers and was instrumental in capturing the city of Troy. Trojans are innocent-looking software programs that appear to be useful but can actually cause significant damage once they get installed in the system. People are often tricked to download Trojans as they appear to have come from legitimate sources. Unlike worms and viruses, this malicious software is incapable of self-replicating. Hence, the damage caused by these programs is not extensive.
Worms -- Internet worms are undoubtedly, the most dangerous form of malicious software that are capable of spreading from computer to computer without any manual assistance. Worms are almost similar to viruses in their design. However, unlike viruses, worms are capable of replicating themselves in the system, and thereby creating multiple copies of the same program. While transmitting, one computer can send hundreds or even thousands of copies of a single worm. Worms consume excessive system memory space due to their replicating nature, and can cause web servers, network servers and hard disks to crash or stop responding.
Viruses - These are malicious computer codes that are capable of attaching to a computer program or a file. Whenever the program or the file is transferred from one system to another, the virus spreads. Computer viruses commonly get attached to .Exe or .Com executable files. Viruses infect the system only when the infected executable file is installed and run. Viruses primarily transform an ordinary program into an unintended Trojan.