What is malicious code? Malicious code is created to intentionally harm computers, systems or other devices. Malicious code often takes the form of a legitimate action, often hidden in application code of a program that performs a legitimate task. This makes malicious code more difficult to eliminate than typical viruses because common antivirus applications are unable to pick up the malicious code until it has been identified and stored in the antivirus database. There are many different types of malicious codes, but the three most common types are viruses, worms and trojan horses.
- Virus: Viruses are basically applications that exhibit harmful behavior once they have been activated. They are often sent via email or posted on websites and forums. Clicking on the contaminated link or opening of the malicious file can infect computers or entire networks.
- Worm: Worms are dangerous pieces of malicious code that can infiltrate computers, damage it and then spread to other computers across the cyberspace. Worms are typically spread by accessing an infected user's address book and emailing replicas of itself to all entries.
- Trojan horse: Hackers and other malicious attackers usually prefer to implement Trojans. A trojan horse is malicious code hidden in legitimate applications. Once an unsuspecting user clicks on the file, the trojan horse springs into action. Since the legitimate action the file was intended to perform is also executed simultaneously, many computer users have no way to know they have been infected until it is too late.