How to secure my server? I don’t want someone to hack my game like Jailbreak
Oop okay my bad then, thanks! 
How would they jailbreak your server?
By validating all data sent through remotes, making sure the client can’t boss the server around in any way.
How i can knoow if client can’t boss the server
Read my reply above about an example of sanity checks. Validate client requests and make sure they make sense. As well if you care about players moving too quick or teleporting, you could have a server script checking player positions and comparing it to the last known position and detecting if they teleported. Though network latency needs to be taken into account with this.
e.g. don’t have the client tell the server how much money something costs, don’t have a remote that kills all players or whatever, etc
I NEVER do that, because i already store player money in leaderstats.
How do i check if player teleport?
i have saw anti exploit of many game
player just got kicked when they fell from high place.
Falling would have to be taken account of as well. The example I provided would be saving positions of players and then comparing them with the new position. This could be in a script on the server that is in this loop.
The issues with this is that I would only recommend kicking players that are obviously teleporting by large values. Though death could be counted as teleporting. You have to be careful with making something like this due to death, falling, and network latency. You don’t want to ban or kick players that didn’t actually exploit or players will get angry. I don’t have a 100% solution but just advice.
Umm. this is so hard to secure my server.
If players have a bad network, other players will just see they teleport…
I have a portal that will teleport portal… very far distance…
then if exploiter teleport just in little bit distance server will look them just innocent
I didn’t know we shouldn’t trust client
my old game just trust client
Is there are no 100% solution?
What kind of game are you making?
I making game type Fighting and Story game
PVP? Or just fighting monsters?
All, i have make the story game too, but i just pause to make it for a while
I read all of your reply
That mean my game failed all security
Player teleport, flying, etc
i have reported he.
One thing to secure your game would be how you handle player to player combat. You need to validate that the player can actually attack another player and do damage to them. Meaning when the client fires the remote to tell the server that the client is attacking another player, you have to validate that. You should check if the player is near by the other player by comparing their positions and getting the distance between the two. If they are close enough then you should check if this type of request has been done before, aka if they are firing it too many times. There are a few ways to approach this, I saw one developer use a leaky bucket approach. This is just to prevent an exploiter from dealing damage that isn’t possible to regular clients.
Player can actually deal damage because i use remote event already.
i don’t know how much distance need to deal damage, using magnitude?
I think it should be a little bit liberal due to network lag. Though you don’t want someone across the map to be able to fire the event and tell the server that he’s dealing damage to someone on the other side of the map and the damage actually happens. The exploiter will always be able to trigger these events but it’s up to you to validate it on the server