Malicious code is a code that takes on various forms (viruses, worms, spyware, Trojan horses, etc.) that is intentionally developed to cause harm to a computer and/or compromise data on a system. Malicious code can also be referred to as malware, which is short for malicious software, but the difference is that malicious code also includes scripts that can take advantage of security vulnerabilities in order to upload malware or do other harmful things.