Trojan-Dropper programs are designed to secretly install malicious programs built into their code to victim computers.
This type of malicious program usually save a range of files to the victim’s drive (usually to the Windows directory, the Windows system directory, temporary directory etc.), and launches them without any notification (or with fake notification of an archive error, an outdated operating system version, etc.).
Such programs are used by hackers to:
secretly install Trojan programs and/or viruses
protect known malicious programs from being detected by antivirus solutions; not all antivirus programs are capable of scanning all the components inside this type of Trojans.