DLL Sideloading is a cyberattack technique where attackers place a malicious Dynamic Link Library (DLL) file in a location where a trusted application will load it instead of the legitimate DLL. This happens because many programs search for required DLL files in specific directories, and if a malicious DLL with the same name as a legitimate one is found first, the program will execute the attacker's code. This method allows attackers to run their code with the same privileges as the trusted application, often bypassing security controls and remaining undetected.