I don’t know all the parameters of safety, but I lost a lot money at https://freelancer.in. There are many or about 30% or profiles are scam here, no safety rules. What I’ve experienced here:
1. Don’t move transfer source code to their server before getting milestone payment.. because few employers change dramatically, they don’t release the payment or give negative feedback after getting complete project code.
2. Create your own milestone at each step of project modules, and ask to release milestone before deploying on server.
3. Don’t trust your employer blindly, do a proper research. Platform like Freelancer doesn’t guarantee anything (neither safety of your money nor reliability of people you are working with/for.).
I am not the only one who would be saying so. I’m working on freelancer since 2014, and found many scammers. I truly avoid few platforms like: Freelancer, Guru..