Null Bind in LDAP configured on CentOS

[skynetonsecurity () gmail com]

Hi Guys,

I am looking for solution on disabling null Bind for  LDAP installed on CentOS?

Is there any way to disable it because while doing Vulnerability assessment for one of the customers I could fetch out 
all the users names with the NT & LM hashes from Domain Controller.( Using (objectClass=*) this filter ) 


Thanks in advance

Em See