FlyTrap is an Android based malware strain that works by stealing cookies. It relies on a few basic social engineering tricks to lure unsuspecting victims to using their Facebook credentials to log into a malicious app. The app harvests the login data allowing the hackers to reuse it later.
This malware strain so dangerous because of the fact that many people make regular use of their Facebook login credentials as a quick and convenient way to log into a variety of other sites. That is even if they haven't actually been on Facebook in a very long time.
Essentially that means that those users are reusing the same password across a great many sites on the web and once the hackers have your Facebook credentials they can, of course, log into any site you've used them on.
According to security researchers, the hackers controlling FlyTrap have been running campaigns since at least March of this year (2021). They're offering highly attractive incentives like Netflix coupons to lure unsuspecting victims to hand over their credentials.
If you see an offer that looks too good to be true ("Login here with Facebook to claim 3 free months of Netflix!" for example) then steer clear. It's entirely possible to find legitimate and completely safe offers like that on the web. All too often it's a trap with means to deny you control over your account. Don't fall for it.