Binwalk is a tool for searching a given binary image for embedded
files and executable code. Specifically, it is designed for identifying
files and code embedded inside of firmware images. Binwalk uses the
libmagic library, so it is compatible with magic signatures created
for the Unix file utility.

Binwalk also includes a custom magic signature file which contains
improved signatures for files that are commonly found in firmware
images such as compressed/archived files, firmware headers, Linux
kernels, bootloaders, filesystems, etc.
More details are available at:

WWW: http://www.binwalk.org