Before starting any substantial assignment, ask two questions in writing: “Will this work be used by the company if I am not hired?” and “Is there a paid option for completing this stage?” A company running a legitimate assessment will answer the first with an unambiguous no. The question is reasonable, and the response tells you something useful either way.
For creative work specifically: submit low-resolution versions, watermark deliverables, or provide a process document and concept outline rather than production-ready files. If the company needs the finished asset to evaluate your work, they needed the asset — not an evaluation.
If you proceed, retain copies of everything submitted with timestamps. If you subsequently identify your work in use by a company that did not hire you, you have grounds for an intellectual property claim. Practical enforcement is difficult, but public documentation — on LinkedIn, Glassdoor, or here — raises the reputational cost of the practice considerably.
Reports on Ghost Jobs Index that describe extraction assignments — specific company, role level, what was asked, approximate scope — help other candidates recognise the pattern before they invest hours in a process that never intended to hire them.