i have 10 servers

how can i prevent ddos attacts?

thanks?

Get more servers.

You can't prevent this type of attack. All you can do is try your best to mitigate it.

Essentially... if you have a 1mbit/sec pipe and your DDoS attacker is pushing 2mbit/sec at that - then you're hosed.
If you have a 10mbit/sec pipe and they can only push 7mbit/sec at you - then you'll be fine.

You can try to contact your/their ISP, block their connections as they come in - but you can't 'prevent' it.