A Remote Access Trojan (RAT) is a malware program that includes a backdoor for administrative control over the target computer.
RATs are usually downloaded invisibly with a user requested program , such as games or sent as an email attachment.
Once the host system is compromised, the intruder may use it to distribute RATs to other vulnerable computers and establish a botnet.
Because a RAT enables administrative control. RATs can be difficult to detect because they usually don’t show up in lists of running programs or tasks.
The actions they perform can be similar to those of legitimate programs. Furthermore, an intruder will often manage the level of resource use so that a drop in performance doesn’t alert the user that something’s amiss