[tptacek]

This is a really old reversing trick, for what it's worth; for instance, pulling gzips out of firmware images, or spotting zipped Java images. You can also often identify cryptography primitives from their ASN.1 OID strings. There are a bunch of tools that do stuff like this.

[virtualmic]

Yes, I use this one regularly: https://github.com/ReFirmLabs/binwalk

(Binwalk is a fast, easy to use tool for analyzing, reverse engineering, and extracting firmware images)