While investigating a malware outbreak on your company network, you discover something very odd. There is a file that has the same name as a Windows system DLL, and it even has the same API interface, but it handles input very differently, in a manner to help compromise the system, and it appears that applications have been attaching to this file, rather than the real system DLL. What BEST describes this?

Shimming is when the attacker places some malware between an application and some other file and intercepts the communication to that file (usually to a library or system API). In many cases, this is done with a driver for a hardware component. A Trojan horse might be used to get the shim onto the system, but that is not described in this case. A backdoor is a means to circumvent system authorization and get direct access to the system. Refactoring is the process of changing the names of variables, functions, and so forth in a program.