Re-post: Stopping illegal robocalling [telecom]

Because of the weak response to my previous posting (2 Feb.2014), I'm once again asking the newsgroup readership to help form a grassroots alliance to get illegal robocalling stopped. The method is detailed in my entry to the 2012-2013 FTC Robocalling contest. See

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I'll give a brief overview here.

In my opinion it will be fruitless to try to stop these calls by threats, making them illegal, etc. This will work only if the callers can be identified and prosecuted easily. Therefore, my proposal relies on technical means to actually stop most calls from completing. The method is based on caller ID (CID) information delivered with the calls. It requires development of new features to be deployed in the phone network.

My proposal works by dividing robocalls into two categories. Category 1 calls are delivered with a valid CID. Here, "valid" means a) the recipient of the call can dial the CID and the call will go to the entity (PBX, etc.) that placed the robocall, and b) the calling entity will have a billing address at which enforcement authorities can find the robocallers if they are pursued because the calls are illegal. Category 2 calls are delivered with a blank or fake (spoofed) CID. It is presumably difficult to get a billing address for such calls. My hypothesis is that most illegal robocalls are in this category.

Category 1 calls cannot, in my opinion, be identified as illegal via technical means (remember that some such calls are not illegal). Therefore I favor a method for recipients of calls to report them (via dialing a new "vertical service code" such as *99) into a new database. Searches of the database on various criteria by enforcement authorities should identify the largest-scale culprits fairly easily.

Category 2 calls must have their CIDs flagged as improper. This must be done by the first switching entity that qualifies as part of the public switched telephone network (PSTN) that a call origination reaches. This switching entity must be configured with a new feature that identifies any customer-provided CID as valid or spoofed. It must be able to do this because it is the same entity that routes calls TO the customer when that same CID is dialed elsewhere on the PSTN. This switching entity must send the valid/spoofed information in the signaling messaging accompanying every call origination. Signaling standards support support this information in a "screening indicator".

Switches that receive calls to be sent to one of their connected phones must also implement a new feature to check the signaling of incoming calls. If the CID was spoofed, the switch simply blocks the call. I propose additionally that the switch itself "answer" the call in order to create a charging record for the caller.

Finally, we need to be aware that some telephone companies may inadvertently or willfully violate their public trust and incorrectly label spoofed calls as valid. For this purpose we need yet another feature to label every telco as trusted or not. My proposal to do this is another database that can be resident within the signaling system. Any call received by a trusted telco from an untrusted telco would have its CID screening indicator flagged as untrusted. If the indicator is untrusted, the switch for the terminating phone can take a variety of actions, including call blocking.

Many more details are given in the proposal whose link is above. I seek comments on the proposal and on how we can get it to happen. Because the economics do not appear favorable for telcos, at least at first, my thinking is that regulatory action is needed. So far, my contacting the FCC has not been successful. I'm considering contacting my congressman next. Constructive comments on both the technical and "political" aspects of this issue are welcome.

[moderator pro tem's note: I discussed this with the poster. It's an interesting concept, and probably would work technically were it implemented and required. The probem is that it requires changing switch software in existing old DMS and 5E switches, and in the SS7 network. That stuff is old, not well supported, and the telcos are just letting them rot in place. So trying to get them to do anything would be extremely difficult. Comments from the rest of the readership are welcome!]
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I would love it if this idea were implemented. Even if it were optional and only a few telcos did it, subscribing to one of them would mean protection from junk calls (at least if you're willing to aggressively block all calls that arrive with untrusted caller ID, except those from whitelisted individuals).

However, I don't expect any incumbent telco to be in favor of it, since their business model demands that all calls go through, including junk.

I expect that the market will solve this problem sooner or later. One way would be for more widespread use of VOIP to replace POTS, after which similar filtering could be done by software on the computer receiving the calls.

Oddly enough, though, the Federal Government has finally done something that may help. Telemarketers are one of about 20 kinds of politically unfavored businesses which the FDIC is now urging banks to stop serving, as part of a nasty federal operation called "Choke Point". See:

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Reply to
John David Galt

I'm all for blocking robocallers. But as Fred, the pro tem moderator, wrote [appended to your Tuesday May 6 article]:

" The probem is that it requires changing switch software in " existing old DMS and 5E switches, and in the SS7 network. That " stuff is old, not well supported, and the telcos are just letting " them rot in place. So trying to get them to do anything would be " extremely difficult. Comments from the rest of the readership are " welcome!

Shoe-horning a solution into the aging existing infrastructure is going to be a very difficult part of achieving the goal assuming legislative support for the task. I wouldn't be holding my breath waiting. :-)

Note your original February 3, 2014, article also cited the IETF in addition to your

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" The main thrust of the proposal is to detect Caller ID spoofing. " For your information, the IETF has resurrected its efforts to " detect Caller ID spoofing. " " Check it out: "

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" " Also available at: "

Out of curiosity, I did some Googling regarding the Ooma VoIP service in this regards and found these 3 URLs with some interesting solutions and thoughts:

  1. View topic - Robocall blocking suggestions. - Ooma
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  2. Want to block telemarketers? Use Ooma's Blacklist feature ...
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    [ noting Ooma Premier has a personal blacklist and a community one ]
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    " " [...] " At the top of the list of most desirable home phone features is " the ability to automatically block unwanted callers. Among " people considering switching home phone service, 77% said a " feature that automatically blocks telemarketers and other " unwanted callers would make them more likely to switch, says " another study conducted by novaQuant, Inc., a leading market " research firm, and commissioned by Ooma, Inc., a leading " Internet-based home phone service. " " Ooma offers this unique privacy feature as part of its Premier " Service via a personal and community blacklist. The Personal " Blacklist blocks specific callers or sends them directly to " voicemail and the Community Blacklist draws on a database of " thousands of known telemarketers and solicitors automatically " blocking those callers. " [...]


Reply to
Thad Floryan

Per John David Galt:

That rings true to me. With VOIP, one can implement challenge-response (i.e. Press 1 for Fred, Press 2 for Sam....).

I'm seriously considering moving my incoming calls to VOIP. I already have all my non-800 outgoing calls going through a VOIP provider. Only reason I haven't gone all the way is that it seems like VOIP providers' implementation of 911 is unreliable.

OTOH, the DNC lists have become moot and we're sometimes getting a half-dozen solicitor calls a day.... so maybe I'll be making the cutover.

Cellphone-wise, I have something called "Call Control" on my Android phone and robocalls and other solicitor calls have dropped off to near zero from a high of several per week.

Reply to
Pete Cresswell

Why not replace caller ID with a non-spoofable variety. I presume this kind of thing already exists in the kinds of records the telephone plant makes.

Or, have your proposed *99 code act not on the CID number but on the actual originating number.

[moderator pro tem's note: It's not that simple. Calls from individual line analog (home-type) phones have an ANI, which is generally accurate, and PBX trunks can have an accurate ANI and a user-generated CID. But robocalls come through a chain of providers, typically VoIP intermediaries, and there is no clear ANI. There are also carriers not delivering ANI to other carriers. It's a mess.]
Reply to
Jim Haynes

A significant aspect of this proposal not emphasized in the re-post is that, assuming PLMN switches are appropriately upgraded, it works for cell phones as well as landlines. I.e., the proposal stops illegal robocalls to cell phones. If we're going to solve the problem, let's do it only once, if possible, for ALL phones.

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