Brother MFC-3420C - Manual (Page 150)

8 - 4 NETWORK SCANNING (MFC-3320CN AND MFC-3820CN ONLY)
3
Click the Scan To Button tab in the dialog box and enter your
PC Name in the Display Name field. The machine's LCD
displays the Name you enter. Default setting is your PC Name.
You can enter any name that you like.
4
You can avoid receiving unwanted documents by setting a
4-digit PIN Number. Enter your PIN Number in the PIN Number
and Retype PIN Number field. To send data to a PC protected
by a PIN Number, the LCD prompts to enter the PIN Number
before the original can be scanned and sent to the machine.
(See Using the Scan key on page 8-5 to 8-9.)