I get enough legit and illegitimate ones every week on LinkedIn that it's become really easy to tell the difference. Hard to pinpoint in a comment because it's mostly a gut feeling. But, in rough order:

1. Look at the person's LinkedIn profile contacting you and examine their post history. In one comical scenario the "recruiter" had a long 4 year gap where they were writing comments in English and all of the sudden they switched to Spanish. Mostly short, pointless comments as well.

2. Look at the company and make sure they have a legitimate website and are still actually in business. Even better, see if there's a public team page that lists this person.

3. Give the recruiter an email (I usually use something like SimpleLogin) and ask them to forward you the details. Of course, pay close attention to what address they send it from.

4. In addition, or alternatively, ask the recruiter for the public job listing (scammers almost always "paste" it into a DM or upload a clearly AI generated PDF doc).

Once you learn the game it's not too hard to start picking up on them. I've made it a game to play along sometimes just for fun. Ultimately, at the end of the day, make sure you report them on LinkedIn. I've had the account disappear within a hour of doing so.

Honestly unless I'm planning on quitting my current job, or if I were unemployed, I just ignore the linkedin.

Sure they spam you with "XX wants to connect", or "I'm awaiting your reply" emails. But real contacts and friends can call/email you, and everybody else can wait six months.

Despite only connecting with actual people I've worked with, not recruiters, I still get "suggested" posts which are slop, and "that happened". The site is a cesspool.