1. A method, comprising: a network device receiving a suspicious computer file addressed to and destined for a target computer, and in response; the network device determining whether a malware protection program is installed in the destined target computer; and in response to determining that the malwar protection program is installed in the destined target computer: the network device modifying, by at least encrypting, the suspicious computer file to make the suspicious computer file unusable by said target computer; and the network device sending the modified suspicious computer file to said target computer.