A simple way of defeating the compiler backdoor attack (imgur.com)

Note that compilation is often not deterministic-- i.e. compile it again (even on the same PC) and you could get different output.

The Tor project struggles with this, and is working on deterministic builds so anyone can verify that the source code actually matches the binaries provided.

See https://blog.torproject.org/category/tags/deterministic-buil... for more information.