Ask HN: How common are fake job postings when searching for jobs online?

I'm researching problems people face when searching for jobs online.

Many people mention fake job postings, duplicated listings, or companies that never respond after applying.

I'm curious how common this actually is.

Have you encountered fake job postings during your job search?

If so, what were the signs that made you realize the job wasn't legitimate?

Did you notice any patterns (for example: certain job boards, suspicious requests, or companies that never replied)?