Legitimate ecommerce websites will often have a "trust mark" on the footer, header, or checkout pages on the website. These marks are accreditations from Internet security bodies (such as Norton, McAfee, TRUSTe, Trustwave), and should give an indication that this website is trustworthy.
Always cross check the name of the developer on legitimate websites or platforms to check if a game is genuine; Use YIMA, a website vulnerability scanner, where you can do website security check for scams, known vulnerabilities and security headers.