git blame will only really help if the backdoor was inserted into the original code (and even then stolen credentials are possible) AFAIK. It&#x27;s fairly easy to imagine a scenario where this is not the case:<p>* Compromised build script - probably under source control as well? 
 * Compromised compiler - If the attackers had this level of access, they probably had enough access to erase logs showing who&#x2F;when the compiler was replaced
 * Binary patch the compiler output - Not impossible (though I suspect unlikely?) that the original source and build system are clean, but the binary is tampered with after the fact.