Docomo Leaked 340,000 Users’ Data to Amazon US Without Consent — 5ch: ‘Like Hell They Deleted It, LOL’

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The story

On September 15, NTT Docomo announced that it had shared the phone numbers and contract plan names of roughly 340,000 users with Amazon.com’s Japanese subsidiary without their consent. The affected users are some of those who signed up online between April 21 and August 20 for a phone plan that includes Amazon membership perks; the cause was a configuration error that meant the consent-confirmation notice for sharing personal data was never displayed during sign-up. Docomo says Amazon deleted the data by September 12, but on 5ch, users expressed shock that such a system for sharing phone numbers and plan names externally even existed, voiced skepticism about whether the data was “really” deleted, and repeatedly compared the incident to other companies’ data breaches and past personal-information leaks.

Published 9/16 (Wed) 0:17 AM

Yomiuri Shimbun Online

NTT Docomo revealed on the 15th that it had shared the personal information of roughly 340,000 users with Amazon.com’s Japanese subsidiary without their consent. What was shared without permission was users’ phone numbers and the names of their contracted phone plans. The cause was a configuration error on Docomo’s end, and the company says Amazon deleted the data by the 12th.

Source: news.yahoo.co.jp / Original article here

What people said

6AnonymousSep 16, 2026 08:15
Shocked that a feature to share phone numbers and plan names externally even existed
49AnonymousSep 16, 2026 08:26
Re: #6
Any place offering a service that partners with an outside company to do something like this — you should assume they're sharing some kind of personal data externally.
You can't link accounts together without sharing personal info.
193AnonymousSep 16, 2026 09:05
Re: #6
They probably tried to get some cloud service or AWS AI to do something and accidentally uploaded a file with personal data in it.
Yeah, that's just dumb.
10AnonymousSep 16, 2026 08:16
If you link with Amazon you get 1% points back on purchases over 5,000 yen, so anyone who already has both accounts is probably linked up already anyway
197AnonymousSep 16, 2026 09:09
Re: #10
That's literally me.
Though I'm pretty sure they never told Amazon my plan name.
207AnonymousSep 16, 2026 09:18
Re: #10
If anything that'd be through d-Points.
You don't even need to be a Docomo member for that, so why would they need to share your plan or phone number?
11AnonymousSep 16, 2026 08:16
Only Docomo would mess up like this
65AnonymousSep 16, 2026 08:30
Re: #11
SoftBank just leaks stuff outright, honestly.
I canceled SoftBank Hikari years ago and I'm still getting sales calls about it.
21AnonymousSep 16, 2026 08:18
> According to Docomo, those affected were some of the users who signed up online between April 21 and August 20 for a phone plan bundled with a discount on Amazon membership fees. Due to a configuration error, the consent-confirmation text for sharing personal data with Amazon wasn't displayed during sign-up.

So these are customers who were already using both services anyway.
Doesn't seem like it did much real harm.
37AnonymousSep 16, 2026 08:23
Re: #21
If this weren't a major company they probably wouldn't have bothered apologizing, disclosing it, or even asking Amazon to delete the data.
78AnonymousSep 16, 2026 08:34
Re: #21
Is this some special deal just for people who've linked their Amazon account ("甘", lit. "sweet", is 5ch slang for Amazon)?
I don't use Amazon, so I'm fine.
210AnonymousSep 16, 2026 09:20
Re: #21
There are 340,000 people who fit that narrow a set of conditions?
24AnonymousSep 16, 2026 08:19
Get ready for the "How about switching to Docomo Hikari?" sales calls
36AnonymousSep 16, 2026 08:22
Re: #24
Lately I keep getting calls like "This is NTT, this is your final notice."
The funny part is they say "your NTT line gets cut off in 3 hours" one day, and then just call again the next day anyway.
27AnonymousSep 16, 2026 08:19
Oh right, Docomo and Prime Video teamed up recently.
This is probably related to that.
45AnonymousSep 16, 2026 08:26
Re: #27
Ah, so this is promo material for that.

https://ssw.web.docomo.ne.jp/prime/
46AnonymousSep 16, 2026 08:26
"Amazon says it deleted the data by the 12th"

Like hell they did, lmaooo
47AnonymousSep 16, 2026 08:26
Wait, is this the d-Points linkage thing? I don't even have a plan tied to that.
Amazon US shouldn't have any linkage set up in the first place, I'd think.
54AnonymousSep 16, 2026 08:27
Re: #47
"Can you use d-Barai on Amazon too? Benefits and setup steps explained"
https://service.smt.docomo.ne.jp/keitai_payment/corporation/shop/tips/ID96.html
101AnonymousSep 16, 2026 08:38
There was also that report on June 25 about the Digital Agency leaking over 246,000 pieces of My Number card personal data here in Japan. The news said to watch out for impersonation emails and phishing scams. This kind of thing is just normal in Japan.
107AnonymousSep 16, 2026 08:41
Re: #101
Especially with Docomo, this is just business as usual, no?
184AnonymousSep 16, 2026 09:01
Re: #101
You'd have to report it as often as the weather forecast before it actually sinks in.
168AnonymousSep 16, 2026 08:56
This is exactly why linking accounts is scary.
The more services you link together,
the higher the risk of a leak keeps climbing.
Humans mess up, that's just a given.
179AnonymousSep 16, 2026 08:59
Re: #168
They only announced it because it's Docomo.
182AnonymousSep 16, 2026 09:00
Re: #168
I think that's right, more linked services means more leak risk.
It's convenient, sure, but trying to connect everything to everything else is asking for trouble.
187AnonymousSep 16, 2026 09:03
Give it ten more years and our personal data will be totally exposed for anyone to see.
Like walking down the street stark naked.
192AnonymousSep 16, 2026 09:04
Re: #187
Bet the bureaucrats and cabinet ministers will still be fully dressed though.
202AnonymousSep 16, 2026 09:13
Re: #187
Honestly, just personal data leaking might be the mild version. If that gets bundled with your trash-talk tweets and your history of buying adult stuff, now THAT'S a scene straight out of hell, lol
199AnonymousSep 16, 2026 09:11
Re: #1
If you couldn't proceed with signing up for this bundled plan without agreeing to it (I forget the exact numbers, but I think this monthly discount might be cheaper than Amazon's own monthly rate — though Amazon's own annual payment, or even YouTube's annual plan, might actually work out cheaper than this) then sure, they should have to disclose that. But either way, the data gets shared all the same, doesn't it?
200AnonymousSep 16, 2026 09:12
Re: #199
"YouTube too" should read "YouTube's" (typo fix)
204AnonymousSep 16, 2026 09:14
Re: #199
My mistake. Since in Re: #1 Amazon had already deleted the data, it might have been possible to proceed with sign-up even without giving consent.

Background and Key Points of This Story

This unauthorized data sharing wasn’t the result of an outside attack — it’s attributed to a configuration error on the sign-up page for the phone plan Docomo offers in partnership with Amazon (the one with discounted membership fees), which meant the consent-confirmation text for sharing personal data never displayed. Those affected were some of the users who signed up for this plan between April 21 and August 20, and only phone numbers and contract plan names were shared; Docomo says addresses and payment information were not included. On the thread, some posts noted that this kind of business partnership isn’t unusual in itself, and that “data sharing necessary for the service” and “failing to obtain consent” are separate issues — while plenty of other voices were skeptical of taking the claim that “Amazon deleted the data” at face value. Many posts also compared the incident to other personal-data cases, such as June’s leak involving My Number cards, framing it not as an isolated scandal but as part of a broader distrust toward the risks of linking personal data with outside partners — a nuance that doesn’t come through in the article text alone.

*This article is compiled and summarized from the 5ch (Breaking News Plus) thread “[NTT Docomo] Personal Data of 340,000 Users Shared Without Consent with Amazon.com’s Japanese Subsidiary… Caused by Configuration Error.”

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