How can i refuse a user ftp to my server ?

[signalsys]

Two users A and B
i allow A to ftp to my server , But B not.
What can i do ?
Thx in advance

 

[kHz]

/etc/ftpusers

 

[khalidaaa]

kHz is right:

Before the ftpd daemon can transfer files for a client process, it
must authenticate the client process. The ftpd daemon authenticates
client processes according to these rules:

*	The user must have a password in the password database, /etc/security/passwd.
(If the user's password is not null, the client process must provide
that password.)

*	The user name must not appear in the /etc/ftpusers file.

*	The user's login shell must appear in the shells attribute
of the /etc/security/login.cfg file.

*	If the user name is anonymous or ftp, an anonymous FTP account
must be defined in the password file. In this case, the client process
is allowed to log in using any password. By convention, the password
is the name of the client host. The ftpd daemon takes special measures
to restrict access by the client process to the anonymous account.

http://nersp.cns.ufl.edu/~dicke3/nerspcs/ftp.html

Regards,
Khalid