Computer viruses are executable code programs that have a unique ability to replicate themselves in computer system and spread rapidly from one computer to another affecting file, documents and programs to alter their normal running. Viruses are represented as patterns of computer instructional codes that exist over time in computer systems. Antiviruses on the other hand are programs specially developed to counter challenges brought about by viruses as they protect the computer systems from virus attacks by heavily relaying on the controls enhanced in their databases. Antiviruses therefore scan the computer using some specific patterns of bytes indicative of known viruses. To stay current, they must be developers of these antiviruses update their databases whenever new viral strains arise. This paper reviews the various virus and antivirus patters and various detection schemes. Today, safety of our data is a big question from various threats come from online and offline. The user should protect their valuable data from these threats using different antivirus software tools available in market. Before going to install an antivirus software tool, the user should know the performance, features, help and support given by the antivirus software tool providers. This analysis will help in this situation.