Claiming_In_Spawn - How is it prevented?

Hi, I run a multiverse server and I just created a Factions world. But people are just doing /f claim in the spawn! I tried to stop this with world guard, making /f claim a blocked command. And this message came up: You cannot claim this land due to your relation with the current owner. I don't really like the message so I was wondering whether there was a way to change it in the config?

If not, is there a way on world guard to set 2 points and make it safe zone, as /f autoclaim safezone isnt very precise.

Please help.