The GTA Online hacker issue is peaking with the recent appearance of the particularly vile and damaging insurance fraud hack. Hackers were present in many GTA Online public lobbies beforehand, granted, however avoiding them has never been as crucial as now. Before, they could cause mild inconvenience, or an unfair temporary ban at worst.
The new hack, on the other hand, allows the cheaters to drain your in-game cash, which due to the Shark Card system may partially have been bought with actual currency. These hackers, as it should be obvious, must be avoided at all costs. And before you ask which platforms they are active on, it's the PC version of GTA 5 you only need worry about — the consoles versions are not affected.
The first and most useful method of avoiding these leeches is also one of the simplest — leave the lobby. Join another session. You might land in a session with a hacker of its own, but you might not.
Staying in a lobby with a hacker has absolutely no merits. They most likely won't be dropping any cash on you and even if they do, it will only get you banned until you run the necessary laps with Rockstar Support.
While you're at it, you might as well group up with a crew or regular group of friends and only join invite-only lobbies. You're a lot less likely to encounter any hacker there, plus playing with a group of people you get used to will enhance the experience.
What's more than likely is that they're there to screw with everyone. These hackers get their fun from trolling legitimate GTA Online players by teleporting them all over the map, dropping various props or vehicles on them or saddling them with respawning hostile clones.
