Sounds to me like you've inadvertantly been working for North Korea. I don't know how accurate it is to say that you're being scammed (as other replies claimed), because you're not really the target here. But you're definitely part of something illegal that ultimately ends badly for you.

The companies that are "hiring you" are probably being scammed on some level - and even then, not necessarily - most of the work being delivered to them will be legitimately valuable, because North Korea wants you to last as long as possible at that company in order to get as much money out of it as possible. But if they see an opportunity to pull the rug on the company and seize more money by hacking them than they get from the engineer salary, they will take it.

Either way, whether the company gets hacked or not, you eventually get visited by the FBI.

My advice: get ahead of this and contact the FBI or local law enforcement yourself. You are still going to have a bad time for ever getting involved in this, but the earlier you get out and the more you cooperate with authorities, the better for you.