Code signing exists because modern operating systems cannot treat every executable as hostile by default. Software needs a way to declare origin and integrity at scale. Signed code gives platforms a practical signal; someone identifiable took responsibility for this binary at the time it was built. Malware succeeds when attackers gain that same signal. Not by breaking cryptography, but by inheriting trust that was meant for legitimate publishers. In most major incidents, what fails is how trust is issued, stored, and operationally protected. This article focuses on that chain. From how a signing key gets compromised, to how a signed malicious payload moves through operating systems, browsers, and security tooling with less friction than unsigned malware. What Code Signing Trust Enables in Practice A valid code signature communicates different things and layers of the stack, but all of them rely on the same assumption. To an operating system, a trusted signature answers two questions: who published this binary? has it been modified since signing? That identity allows the OS to apply reputation systems, publisher allowlists, driver loading rules, and SmartScreen style heuristics. Unsigned binaries do not get those privileges. Browsers use signatures as part of extension vetting, update authenticity, and […]
