I can’t imagine why would give cash to a recruitment agency, to be honest, but apparently plenty of people do:

Another scam recruiter – TEFLjobsworld

A genuine recruitment agency will make its profits from the employers, not from the job seekers. You have to be very careful about any TEFL recruitment agency, but not sending money will obviously filter out most of the actual scams. The only other major fraud risk is identity theft, so also be careful about when and to whom you send copies of passports etc.

Same goes for employers. Don’t send them money, and also be suspicious about who they ask you to send money to (e.g. particularly travel agents for flights). They should cover all visa expenses for you, and if they don’t (e.g. it’s a volunteer gig) then you should be paying the local embassy, not the employer.  There are a few genuine exceptions to this rule, but you should make sure that you are in contact with (real) teachers who have been through the same process before you pay a penny.

Ditto for personal information. Only send originals of degrees, copies of passports etc if and when you really need to. There should be plenty of information online about what the standard processes are.