A virus is a computer program that replicates itself by modifying other computer programs and inserting its code. For the replication to succeed, users must, unintentionally, execute the file that contains the virus. Areas within the computer that are affected by the virus can malfunction. On a large scale, computer viruses can result in considerable financial or economic damage to an organisation or entity. Systems are initially infected with the virus through social engineering deceptions, which allow attackers to exploit unpatched security vulnerabilities. A variety of mechanisms are employed in infecting new hosts, with a vast majority of viruses targeting Microsoft Window systems.