Many fake ISO archives are password-protected RAR files. To get the "password," you must complete a survey, install a "download manager," or enter your credit card info. This is a classic social engineering scam.

was never released for the PlayStation Portable. It was developed for:

You download a file named GTA_4_PSP_FIXED.iso . When you double-click it (or try to transfer it to your PSP), your antivirus lights up. You’ve just downloaded a trojan that steals saved passwords from your browser.

— any file claiming to be one is fake. Play the real PSP GTAs instead, use legal ISOs from your own UMDs, and fix emulation issues with proper PPSSPP settings.

To be direct: