Secure Access

		Secure Access

Secure access is a feature of the modem that permits you to restrict access to your system by password protection or by dialling a remote system back on a pre-determined number. This feature is available in both error corrected and non-error corrected modes, but is not available in the fax mode of operation. The secure access feature has two levels of operation. Level 1 access can be used on its own, Level 2 access must be used in conjunction with Level 1.

The modem has a 20 entry dial back store held permanently within its memory. Each entry consists of a password (which must be between 6 and 12 characters in length) and an optional associated dial string (up to 40 characters in length).

Level 1 access

When the modem is set to automatically answer incoming calls, level 1 access provides a means by which admittance to the DTE is protected by a pre-defined password. After a call is successfully established, the remote User is prompted to enter a password. For example:

CONNECT 14400

ENTER PASSWORD:

The remote User is allowed three attempts to enter a correct password. If no password is entered within a short period of time, the ENTER PASSWORD prompt is issued again. If all attempts fail, access is denied and the call is terminated. A message is output to the local DTE as follows:

WRONG PASSWORD

Note: Password characters are shown as an asterisk at the DTE.

If a valid password is received, the remote user is allowed access to your system and normal data transfer may then take place. However, if after receiving a valid password there is an associated dial back number, level 2 access commences.

Level 2 access

Entry of a valid password prompts your host modem to disconnect the remote system and then dial a number associated with the password. The local DTE displays the message:

CALLBACK IN PROGRESS...

Your modem attempts to dial back a preset telephone number. The answerer of this call then gains access to your system.

Using secure access

To use secure access, it is suggested that the following steps are followed:

Compile a list of users with their appropriate passwords and dial back telephone numbers.
Enter each one using the *P command.
Note: Only include a second colon and dial back number if level 2 access is required. For example:
AT*P0:SELENE:01274123456 <Return>
Once you have made all the entries, you should check them by typing AT*L <Return>. This command displays all entries in the dial back store:
AT*L <Return>
0-SELENE:01274123456
1-ICEBERG
2-JUNIPER:Z01272213487
3-WILLOW:T01343320981
etc.
If any mistakes have been made (such as the Z in the dial string of entry 2) then they can be overwritten by repeating the entry.
Make sure that the modem is set up as you require i.e. automatic answer enabled, error correction enabled if needed, flow control, DTE speed etc.
Finally, to enable secure access, you must enter:
ATS80=129 <Return>
ATZ <Return>

With secure access enabled, the modem behaves in a slightly different manner when answering a call. Normally, the modem raises the DSR (data set ready) control line on the serial interface during the modem handshake and then raises DCD (data carrier detect) and sends a CONNECT message at the end of the handshake. With secure access, however, DCD remains in its off-line state until free access is granted to the User. To disable secure access, you should enter:

ATS80=1 <Return> followed by

ATZ <Return>