Malware
Malware (a portmanteau for malicious software) is any software intentionally designed to cause damage to a computer, server, client, or computer network. Malware does the damage after it is implanted or introduced in some way into a target's computer and can take the form of executable code, scripts, active content, and other software. The code is described as computer viruses, worms, Trojan horses, ransomware, spyware, adware, and scareware, among other terms. Malware has a malicious intent, acting against the interest of the computer user—and so does not include software that causes unintentional harm due to some deficiency, which is typically described as a software bug.
Remote access trojan
A Remote Access Trojan (RAT, sometimes called Creepware) is a type of malware that controls a system through a remote network connection. While desktop sharing and remote administration have many legal uses, "RAT" connotes criminal or malicious activity. A RAT is typically installed without the victim's knowledge, often as payload of a Trojan horse, and will try to hide its operation from the victim and from security software and other anti-virus software.