larry@uunet.uu.net (Larry Lippman) (08/08/89)
In article <telecom-v09i0277m04@vector.dallas.tx.us> dl@mthvax.cs.miami.edu (David Lesher) writes: > For a long time, in the 216 (and some other areas, too) 200+7d got you the > ANI computer that read you back the assignment of the pair you were on. The > exception was if the 7d you dialed was correct, it just beeped. This let the > installer confirm the pair he had picked was the correct one. > Recently Ohio Bell changed the code to be 200+ some secret 7d, and let the > troops know that revealing the secret was cause to be terminated. Do any > Digest readers have ideas on the logic behind the policy {if any;-{) The logic is very simple: keeping ANAC (Automatic Number Annoucement Circuit) "secret" or otherwise controlled is believed to hinder any would-be eavesdropper from easily identifying the subscriber line pair of a potential victim. ANAC is a pretty useful adjunct to any perpetrator bent upon unlawful eavesdropping, with such a perpetrator not having access to outside plant pair assignment records. Lacking specific pair data can make such subscriber line identification a trial-and-error task of considerable proportion, and with some risk of discovery. There are basically two methods of such pair identification: (1) Connect a VLF (20 kHz or so) oscillator across the subscriber pair at the known premises location to place an inaudible identification signal on the pair. Using a sensitive receiver and capacitively coupled test probe the pair appearance at a dedicated plant access or control point can be located. This type of equipment is readily available for legitimate telephone company cable tracing purposes. (2) Pick a working pair and dial the subscriber line in question when it is believed that no one is in the premises. Using a high-gain amplifier with capacitively coupled test probe, ringing pairs at the access or control can be identified. Since more than one ringing pair may be detected, the process will have to be repeated until it is certain that the desired pair has been identified. Both of the above methods result in some risk of detection, either at the subscriber premises or through ringing of the subscriber telephone. Successively trying ANAC on pairs using insulation-piercing test clips is much "safer". As an amusing aside, the legendary eavesdropper of the 1950's and early 1960's, the late Bernard Spindel, bragged about using the ringing pair technique on multiple cross-connect boxes (large numbers of bare binding posts - before days of dedicated plant). He would dial the subscriber line, wet his fingers, and "scan" the exposed binding posts for the ringing voltage shock! Most operating telephone companies, especially the BOC's, go to great length to protect subscriber line pair information from unauthorized access - especially by their own employees. New York Telephone, as an example, provides NO reference files to specific subscriber identity and pair assignments in any "unattended" central office; the only exception are special circuits such as WATS, FX, data, etc. which may require periodic maintenance. Pair assignment information is strictly on a "need to know" basis that is made available only with an installation order or trouble ticket - which is the way it should be. ANAC is too useful for telephone company purposes to eliminate or overly restrict out of deference to security issues. Therefore, control of ANAC access is attempted made through "intimidation" of craftspersons not to reveal the number. In addition, some BOC's with ESS offices routinely place the ANAC code on "call trace", which specifically records the date, time and calling number of all ANAC requests. If ANAC "abuse" is suspected, the ANAC access records can be extracted from call accounting tapes. Furthermore, since ANAC is most commonly used NOT for outside plant purposes but at the central office MDF (Main Distributing Frame), some CO's have the ANAC circuit connected to one or more loudspeakers located in the MDF area. It is more convenient in routine cross-connection verification for a frameperson to dial the ANAC code with a butt set and hear the result without having to put the butt set to their ear. In some CO's, the ANAC annoucement is ONLY connected to loudspeakers in the MDF area, and there is NO audible annoucement on the pair itself; this is considered a "security" measure. The moral of the story is that, today, ANAC usage may well be monitored. What the telephone company can DO with ANAC usage information is another matter, but they CAN and DO monitor it. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"