US Patent 7607171 Virus detection by executing e-mail code in a virtual machine

An intermediary isolation server receives e-mails and isolates any viral behavior from harming its intended destination. After the intermediary receives an e-mail, it determines that the e-mail has associated executable code, and then identifies the environment in which the e-mail code would be executed if delivered. The intermediary then executes the code by emulating how it would be executed in its ultimate environment. If a viral-like behavior is detected, appropriate action is taken to prevent the execution of the code at its intended destination. The attachment is executed in a contained environment that allows for the contained environment to be easily restarted in a clean state.