some of my friends have network near of me tell me that some clients hack his network by change Mac address( by any program like MacMakeUp.exe) and hac any active user ; after than they can access net with no problem., he have mt ver 3.3 and asked me many time how to solve that problem? And I have mt ver 5.10 on RB750 can this hack happen with me also ???

are you talking about wireless clients? if so, it is a good idea to implement WPA encryption on wireless

That’s happen in the both network cable and wireless.

for wireless you need to use WPA encryption
for ethernet you need to use encrypted PPPoE

then this will not be possible

There's nothing new about this. It's the flaw of mac based authentication systems and it's been around for quite a while now. The only way to resolve it is to use a different authentication method that requires a sign in and is encrypted.