The purpose of Trojan Droppers, as the name suggests, is to install malicious code on a victim’s computer.
They either install another malicious program or a new version of some previously installed malware.
Trojan Droppers often carry several completely unrelated pieces of malware that may be different in behavior or even written by different coders:
in effect, they’re a kind of malware bundle containing many kinds of different malicious code.
They may also include a joke or hoax, to distract the victim from the real purpose of the Dropper, the background installation of malicious code, or adware or pornware programs.
Droppers are often used to carry known Trojans, since it is significantly easier to write a dropper than a brand new Trojan that anti-malware programs will not be able to detect.
they are, therefore, easy to write and can be used to perform multiple tasks.