It's really, really bad. We post a role, get 500 applicants, and nearly all of them are not legitimate. They all look amazing, really great resume, impressive LinkedIn, etc... but when you dig a little deeper, it's not that hard to find a bunch of red flags (LinkedIn profile create < 3 months ago, VOIP number, using VPN to submit job application, etc). You really have to know what signs to look for. They're very convincing fakes.
We're extremely vigilant about this issue as a company, yet we've had people get through 2 or 3 rounds before someone realized something was off (some people are really, really good at faking it).
I feel bad for small companies trying to hire. For us, it got to the point where we literally couldn't open a role unless we had a full time recruiter to sift through all the international candidates pretending to live in the US.
Edit: We've been dealing with this for a couple years now, and there still isn't a great solution. Unfortunately the only surefire "solutions" we can think of are also things that would make the interview process less enjoyable for real candidates, which sucks. (One idea was to ask candidates to show us photo ID during the video interview, but something about making a candidate do that just doesn't feel good - although we have tried it, and it has effectively stopped a few fake people from getting through)