Asad, if you are literally talking about authenticating the candidate to be sure the candidate on the resume is the same person (candidate) on the phone screen and is again the same individual on the final skype call and is the same person who shows up to perform the work i would say this:
1. the candidate and/or his/her 'handler' (often the company sponsoring the candidate's visa if we are talking about foreign workers being screened and hired for temp IT projects here in the US - please clarify) are crooks and they should be reported to the authorities.
2. consider starting a service (think "eTrust" for recruiters) or an association of recruiters whereby you and the members can help identify and weed out the unscrupulous agencies/handlers. I will charge only a small equity fee for the idea :-).
3. money is the motivator here so the most effective way to protect the customer is via an effective contract that provides for financial penalties for fraud/misrepresentation.
4. The candidate and his/her handler need to be notified from the start that fraud or dishonesty will not be tolerated. Having the handler provide the candidate's visa photo and visa ID# at the start will put them on notice.
5. Put a financial burden of proof on the candidate's handler. That could be, for example, the handler is responsible for travel and other expenses and the first 14-30 days wages for the candidate which will be reimbursed to the handler upon confirmation that the person who shows up for work is the correct person. If not then the person is sent back with no financial obligation other than the handler being responsible to pay the candidate's wages, taxes, etc.
5. I would consider requiring that the handler provide a copy of candidates visa photo and visa ID# with the resume and all subsequent interview steps should be via skype so the interviewer can make a visual confirmation. This doesn't address the use case where the resume does not belong to the person who shows up on camera, but this is addressed in the contractual terms and the tech screener should be able to ferret out any discrepancies.
6. with the visa ID# any confirmed or suspected fraud can be reported to ICE (immigration and customs enforcement). The handlers are often on visa's themselves and if not they still understand that they can be tracked down as the visa sponsor.
7. don't forget us little guys when you strike it rich!
What you want is to prove someone's identity in a way that ensures they are accountable.
There is no magic to tell if someone cheats somewhere along the interview process but since January of 2020, it now is possible to prevent posing or masquerading as someone else, and this effect is very powerful.
TruAnon lets people verify themselves using online stuff they already have, and without using any private or regional information so it works just the same for anyone even if you don’t have any ID at all.
This means you can BAN a person and retain their confirmed identity such that they cannot return with another email or a fraudulent identity.
Once you assure that outcome, fraudulent intent is dishearteningly thwarted to the point where there is just no point in trying to game the system.
If you are operating a gig-economy site, job site or a prestigious networking community such as this one here, you should consider automatic verified identity because it creates a sense of safety, authenticity and quality.
Plus, people just prefer to avoid invasive procedures and risking humiliating loss of privacy so common in background and credit checks we use today.