Importance of Null user in hacking

A null user is basically a pueudo-account that has no username or password but can used to access certain information of the network.
The null user is capable of enumerating account names and share on domain controllers,member server and workstations.
Null user connection can get established with any computer having a netBIOS connection.
The CIFS/SMB and netbios standards in windows 2000 include API that return rich information about the machine via tcp port 139-even to the unauthenticated users.

Some of the good tool that helps in creating an enumeraton of user name and password by using a null session are
1)dump sec
2)nbstat
3)enum downloadable from site http://razor.bindview.com
4)getacc downloadable from site http://www.securityfrida.com


Counter measures for null sessions
disable SMB services entirely on indivisual hosts by unbinding the wins clicent TCP/ip the interface.

editing in registry

HKLM/SYSTEM/CURRENTCONTROL SET/LSA
CHOSE EDIT |ADD VALUE
VALUE NAME :RESTRICT aNONYMOUS
DATA TYPE:REG_WOOD
VALUE 2