Implementation of an ICMP-based covert channel for file and message transfer

Covert channels exist in most communications systems and allow individuals to communicate truly undetectable. However, covert channels are rarely used due to their complexity. This article presents a novel covert channel based on record route IP header options for downloading and uploading text files and sending short messages. The presence of hidden texts and messages exchanged over the proposed covert channel will be unnoticed unless the IP header options are inspected. A tool has been implemented based on the proposed covert channel. It uses a client/server technology to offer a hidden version of the well known file transfer protocol (FTP) service. This service is called hidden file transfer protocol (HFTP). In addition, the tool offers a hidden SMS service (HSMS) allowing to send hidden short messages.