Final answer:
Malware programs that disguise themselves as system files are known as rootkits. They differ from Trojans, viruses, and worms by being more deeply embedded into the system to hide and manage their activities.
Step-by-step explanation:
Malware programs that masquerade as system files are called rootkits. A rootkit is a type of malicious software designed to gain unauthorized access to a computer and often hides its presence or the presence of other malware. Unlike Trojans, which are typically standalone malicious programs that pretend to be benign applications, rootkits are embedded deep into the system to intercept and modify standard system functions to conceal other malware, can facilitate remote control, and remain undetectable to users and most antivirus software. Traditional malware like viruses and worms may also be present on infected systems, but don't typically possess the same level of stealth and system integration as rootkits do.