Steganography embeds a secret message in an innocuous cover-object. This paper identifies three cover-specific redundancies of executable programs and presents steganographic tecniques to exploit these redundancies. A general framework to evaluate the stealth of the proposed techniques is introduced and applied on an implementation for the IA-32 architecture. This evaluation proves that, whereas existing tools such as Hydan are insecure, significant encoding rates can in fact be achieved at at high security level.