Denial of service attacks apparently from UUNET Netblocks

Jay R. Ashworth jra at
Tue Oct 7 20:01:34 UTC 1997

On Tue, Oct 07, 1997 at 11:43:24AM -0700, ken emery wrote:
> One question, "can't the sender (aka the person initiating the call) 
> forge the ANI information?"  I know on a cisco (1003 series) it will 
> croak if this is incorrect, but what about an Ascend or other ISDN 
> device?  Unless things have changed I don't think the TELCO's in the 
> USA guarantee the ANI is correct.

In short: no.

It's exceptionally difficult to forge ANI, with one small exception.
_Some_ originating end-offices apparently don't validate ANI
information handed to them by PBXs...  otherwise, spoofing ANI requires
intercepting the loop to the receiving sub, or subverting the switch.

This was discussed at length in one of the telecom newsgroups, about 4
months ago, search for "ANI spoof" or "CNID spoof".

-- jra
Jay R. Ashworth                                                jra at
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