Backdoor: A program whose primary purpose is to allow a threat actor to interactively issue commands to the system on which it is installed.
Credential stealer: A utility whose primary purpose is to access, copy or steal authentication credentials.
Downloader: A program whose sole purpose is to download (and perhaps launch) a file from a specified address, and which does not provide any additional functionality or support any other interactive commands.
Dropper: A program whose primary purpose is to extract, install and potentially launch or execute one or more files.
Launcher: A program whose primary purpose is to launch one or more files. Differs from a dropper or an installer in that it does not contain or configure the file, but merely executes or loads it.
Ransomware: A program whose primary purpose is to perform some malicious action (such as encrypting data), with the goal of extracting payment from the victim in order to avoid or undo the malicious action.
Other: Includes all other malware categories such as utilities, keyloggers, point of sale (POS), tunnelers and data miners.