modem
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... security
architecture. For example, having a strong policy with regard to
Internet access and having weak restrictions on modem usage is
inconsistent with an overall philosophy of strong security
...
... Modems ...
... Modem Lines Must Be Managed ...
... can also provide an effective detour around the site's firewalls.
For this reason it is essential to maintain proper control of modems.
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...
Don't allow users to install a modem line without proper
authorization. This includes temporary installations (e.g., plugging
...
... authorization. This includes temporary installations (e.g., plugging
a modem into a facsimile or telephone line overnight).
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Maintain a register of all your modem lines and keep your register up
to date. Conduct regular (ideally automated) site checks for
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... register up
to date. Conduct regular (ideally automated) site checks for
unauthorized modems.
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... easy to intercept messages to cellular phones. Modern high-speed
modems use more sophisticated modulation techniques, which makes them
somewhat more difficult to monitor, but it is prudent to assume that
hackers know how to eavesdrop on your lines. For this reason, you
...
... It is helpful to have a single dial-in point (e.g., a single large
modem pool) so that all users are authenticated in the same way.
...
... bypassed.
At a minimum, make sure that the return call is never made from the
same modem as the incoming one. Overall, although call-back can
improve modem security ...
... same modem as the incoming one. Overall, although call-back can
improve modem security, you should not depend on it alone.
...
... incoming call until the user has typed
in a password). This effectively simulates a dead modem.
...
... authenticated one. The
goal here is to prevent callers using your modem pool as part of a
chain of logins. This can be hard to detect, particularly if a
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...
At a minimum, don't allow the same modems and phone lines to be used
for both dial-in and dial-out ...
... Make Your Modem Programming as "Bullet-proof" as Possible ...
...
Be sure modems can't be reprogrammed while they're in service. At a
minimum, make sure that three plus signs won't put your dial-in ...
...
Program your modems to reset to your standard configuration at the
start of each new call. Failing this, make them reset at the end of
...
... start of each new call. Failing this, make them reset at the end of
each call. This precaution will protect you against accidental
reprogramming of your modems. Resetting at both the end and the
beginning of each call will assure an even higher level of confidence
that a new caller ...
...
Check that your modems terminate calls cleanly. When a user logs out
from an access server, verify that the server hangs up the phone line
properly. It is equally important that the server forces ...