A tutorial I wrote on bypassing AV signature-based detection was published in a Israeli information security magazine called Digital Whisper. In this tutorial I demonstrate several techniques to bypass signature-based malware detection, and as a bonus demonstrate these techniques to bypass Symantec AV from detecting ZBot (Zeus worm).
The PDF version of the tutorial can be downloaded from here:
http://www.digitalwhisper.co.il/files/Zines/0x10/DW16-2-SignatureDetectionBypass.pdf