Abstract: A method of containing the spread of computer viruses provides a registered computer user with an early warning of a potential virus threat in advance of execution of suspected e-mail attachments. Internet users sign up to become a registered member of a virus warning service administered by a service provider. Each member of such service is instructed to enter one or more unique identifiers, such as, for example, designated addresses in their address book and/or buddy list. Such designated address is advantageously an address of the service provider dedicated to receiving e-mails sent unintentionally by members, such that if an e-mail is sent to the designated address from a registered member of the virus warning system, it can be reasonably assumed, or at least suspected, by the service provider of the virus warning system, that such e-mail has been sent as a result of an infected file.