Difference between virus and Trojan
Virus vs Trojan:
Computer systems are very delicate things that can be subjected to various malfunctions caused by various malware which harm the system. There are many types of such malware existing in the world, of which virus and Trojan are two of the most notorious ones. However most of the time, the difference between a virus and a Trojan are not properly identified and therefore, one is seen to be blaming the adverse effects of a Trojan on viruses, assuming the culprit is a virus and seeks to remedy the virus without recognizing the real problem first.
What is a virus?
A virus is capable of attaching itself to a certain program or a file in the computer and spreading itself across various computers and various programs as a result. Another computer can be infected with the same virus if a virus infected file has been copied to another healthy computer. Computer viruses do not always cause the same amount of trouble as their severity can differ from one virus to another. While some may hinder the functioning of the computer, others may harm hardware, software or certain files in the computer. Viruses are always attached to an executable program which indicates that a virus cannot affect the computer unless the file that contains the virus has been opened. Once infected, the virus can spread unconsciously through files, emails or sharing of certain items which have been infected with the virus.
What is a Trojan?
Just like the mythical Trojan horse, the Trojan tends to be very deceiving. It appears to be full of useful programs and yet, once installed, it can cause major harm to the computer. Appearing to have legitimate files from a trusted source, the Trojan cheats its users, destroying files and the information system once it has been installed. However, the damage caused by different Trojans may vary greatly. They often create a backdoor in the system and allow malicious users access to the computer, thus allowing confidential or personal information to be compromised.
What is the difference between Trojan and virus?
A Trojan and a virus are both malicious software which create unwanted problems within the information systems. However, a virus imitates a real world virus by being able to infect any file or system that it comes in to contact, thus moving about from files to file and computer to computer. A Trojan on the other hand disguises itself as the mythical Trojan horse as a useful application and thus, once the user executes its code, it infects the system. But unlike a virus, a Trojan is not able to propagate or replicate themselves. Thus Trojans remain passive unless the user copies them to the hard drive. A virus, however, uses another executable file as a host file and whenever it is accessed, the virus activates itself and searches for other files that can it can infest.
Coding a virus is considered as rather complex work as it is rendered necessary for a virus to program its mechanism in such a way that enables it to attach itself to another file without making it unusable. On the other hand, coding a Trojan is said to be much easier. A batch file which deletes files in the hard drive without prompt which is then renamed into some other application is already a Trojan. Once the user runs this application, it once again starts deleting all the other files as well.
A virus is said to be easier to detect with advanced heuristics in an antivirus program as it has a general pattern of attaching a copy of itself to a new host which allows users to detect suspicious activity. A Trojan, however, is much harder to detect by an antivirus program until AV makers have identified them as Trojans.