Some companies have security departments that analyze malware that targets their employees or the users of their services. Penetration testers might also use re

Some companies have security departments that analyze malware that targets their employees or the users of their services. Penetration testers might also use reverse engineering because people who hired them don't have the source code of some relevant thing, or because they want to see what an attacker who didn't have it could do, or because for some kinds of attacks looking at the actual binary might be more informative than looking at source code. There are also antivirus developers who reverse engineer malware that doesn't necessarily target a particular class or group of users. I've also met a reverse engineer who works with cases where proprietary software publishers have lost their old source code (this is really a thing!).