It's when someone gets a file sent to them and they download it. The host who gave the person the rat can then get all of your information on your computer such as passwords and more! They can gain control of your pc and even can turn on your webcam. Pretty serious business and if you have a card on your pc or any money.. GG
Remote Access Tool(RAT): Remote Administration Tool also known as RAT is used to remotely connect and manage single or multiple computers. RAT is one of the most dangerous Trojan because it compromises features of all types of Trojans. It provides an attacker with nearly unlimited access to host computer along with Screen Capture, File management, shell control and device drivers control. RATs uses reverse connections to connect remote system and hence are more likely to remain undetected. They can hide themselves in process space of legitimate program and hence never appear in task manager or system monitors.