Synopsis From the early days of cracking passwords and stealing information from personal computers to deadly Internet based attacks that can shake the security of an entire nation, cyber crimes have evolved from the endeavors of entertainment by cyber kiddies to the acts of organized crimes and terrorist activities of cyber mafia. Virus attacks, hacking, browser hijacks, spam, DoS attacks, Phishing, Pharming, traffic analysis and so on, are various manifestations of malicious activities that have evolved on the Internet in the last couple of decades. Malware is one such tool that has emerged as a widely preferred choice to consummate criminal activities on the Internet. Malware (malicious software) is a new genre of hostile software, written in a high level language. They essentially target technical vulnerabilities in the system, at network level or at OS level, and exploit human factors like greed, unawareness, and complacency. Spyware, adware, trojans, virus, worms, exploits etc., are very common forms of Malware prevalent on the Internet. It propagates using e-mails, IM and chatting applications, and other web services. Malware can be categorized into criminal Malware and business Malware. The former is used in cyber terrorism and vandalism, while the latter is used for business or monetary benefits.