Suspicious Traffic Hits Japan’s e-Tax System, National Tax Agency Suspends Operations — 5ch: “Things Would Get Interesting If It Got Hacked”

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The story

On November 4, Japan’s National Tax Agency suspended operations of its electronic tax filing system, “e-Tax,” after detecting suspicious external communications. No leak of taxpayer information has been confirmed so far. On the forum thread, numerous users reported having long received phishing emails impersonating e-Tax, fueling speculation about “where the login credentials leaked from.” Many voiced concern over the risk of high-income earners’ addresses and income data being exposed, and one reply told users planning to switch back to paper filing that “it’s pointless, since it all gets digitized via your My Number anyway.”

Nov. 4 (Wed), 20:21 JST — Jiji Press

The National Tax Agency suspended operation of its electronic tax filing and payment system, “e-Tax,” on the 4th after detecting suspicious communications from an outside source.

So far, no leaks of taxpayer information or the like have been confirmed.

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

What people said

4AnonymousNov 4, 2026 23:31
I've been getting a bunch of weird envelopes about taxes too, but they're obviously scams so I just ignore them
41AnonymousNov 4, 2026 23:41
Re: #4
Sounds like you're a prime target for scammers. Watch out — eventually someone posing as an official will show up at your door spouting stuff like "under Article Whatever of the National Tax Collection Act…"
98AnonymousNov 4, 2026 23:59
Re: #4
Is it true that "black" is the last one to show up?
118AnonymousNov 5, 2026 00:09
Re: #4
That color scheme looks like Louis Wain's paintings as his schizophrenia got worse (the artist famous for cat paintings that grew increasingly psychedelic as his mental illness progressed).
9AnonymousNov 4, 2026 23:32
If the KSK system got hacked, that would get interesting (KSK = the National Tax Agency's core integrated tax-data system).
124AnonymousNov 5, 2026 00:11
Re: #9
Apparently it's been upgraded to "KSK2," now with AI built in.
12AnonymousNov 4, 2026 23:33
The one that's been going around a lot lately
13AnonymousNov 4, 2026 23:33
If you're gonna hack something, hack politicians' PCs instead — leave ordinary taxpayers out of it.
166AnonymousNov 5, 2026 00:34
Re: #13
(;゜Д゜) Seriously, this.
21AnonymousNov 4, 2026 23:34
I'm doing next year's tax return by hand. But when I went to the tax office for this year's filing, they told me paper form distribution is getting cut back starting next year — guess I'll have to go stock up on forms.
70AnonymousNov 4, 2026 23:49
Re: #21
You'll lose your deduction if you do that.
30AnonymousNov 4, 2026 23:37
There's so much spam pretending to be the National Tax Agency's e-Tax that I bet someone fell for it, logged in through that, and that's how all this went down.
32AnonymousNov 4, 2026 23:38
Re: #30
Some days I get three or four of them.
40AnonymousNov 4, 2026 23:40
Re: #1
This is exactly the kind of info the "tokuryu" (loosely organized, ad-hoc crime rings recruited over social media) would love to get their hands on.

If this leaks, you're basically guaranteed to get robbed.
51AnonymousNov 4, 2026 23:43
Re: #40
They'd have free rein over your personal info too.

Sounds like you'd get a threatening call telling you to pick whether you want to be the robber or the one getting robbed.
58AnonymousNov 4, 2026 23:46
Glad I stuck with paper filing.

That was close.
81AnonymousNov 4, 2026 23:51
Re: #58
Doesn't matter — it all gets digitized under your My Number anyway.
59AnonymousNov 4, 2026 23:46
Re: #1
By the way, if this actually gets breached, NTT Group is going to lose a lot of credibility — NTT Data handles the system maintenance.
148AnonymousNov 5, 2026 00:22
Re: #59
Is that why the stock's been falling?
155AnonymousNov 5, 2026 00:27
Re: #59
Didn't NTT Data already get hit before?
68AnonymousNov 4, 2026 23:48
Anyone who still uses this stuff is a fool — they clearly have no idea how far behind Japan is on IT.
74AnonymousNov 4, 2026 23:50
Re: #68
Thing is, starting the year after next, if you don't use it you'll lose out on hundreds of thousands of yen, so everyone's going to be forced to use it whether they want to or not. That's the downside of going digital.
75AnonymousNov 4, 2026 23:50
Every other company that gets targeted just ends up breached, but the Tax Agency actually managed to shut this down before anything leaked — impressive.
97AnonymousNov 4, 2026 23:59
Re: #75
They're running the latest American AI — saw it on Prime News.
79AnonymousNov 4, 2026 23:51
Yesterday I got a letter from the tax office saying the password-login method is getting discontinued next year and that I need to get a My Number card. No thanks.
104AnonymousNov 5, 2026 00:03
Re: #79
Can't be helped — guess it's back to hauling piles of paperwork to the tax office every year.
89AnonymousNov 4, 2026 23:54
I've got a ton of these in my spam folder lol
"Your taxes are [unpaid]" (typo in the original — 美濃 "Mino," a place name, instead of 未納 "unpaid")
"You have a refund."
"The deadline to claim it is coming up."
Funny to look at these once in a while.
The format hasn't changed one bit in 20 years, it's hilarious.
All that high-tech hacking just to get personal info, and it ends up used for garden-variety spam mail lol
105AnonymousNov 5, 2026 00:03
Re: #89
That's what hacking actually is — they steal your login info from phishing emails like that, log into the system with it, then try all sorts of things from there.
Enough people fall for it that you can't just laugh it off.
107AnonymousNov 5, 2026 00:04
Even if your tax return leaks, it's basically just like the old published "rich list" rankings, right?
119AnonymousNov 5, 2026 00:10
Re: #107
No way, having your income exposed to the whole world is the worst of the worst. It's on the same level as going bankrupt and ending up on one of those "bankruptcy maps."
131AnonymousNov 5, 2026 00:14
Re: #107
People rich enough to make the "rich list" can afford to hire security guards. The dangerous cases are the halfway-wealthy folks.
112AnonymousNov 5, 2026 00:07
Re: #98
Apparently the one in the bottom right is the last one.
158AnonymousNov 5, 2026 00:31
Re: #112
"Black" is just the weakest of the Four Heavenly Kings (a stock anime/game trope — the weakest member of a villain's top four enforcers)
183AnonymousNov 5, 2026 00:53
Re: #158
There's always someone above you — no wait. There's always someone below you too, huh.
215AnonymousNov 5, 2026 01:36
Re: #158
What level is the middle one in Re: #4's right-hand column?
122AnonymousNov 5, 2026 00:10
Is there even anything in e-Tax that would be a problem if it leaked? Just your address and My Number, maybe?
126AnonymousNov 5, 2026 00:13
Re: #122
For high-income taxpayers, having their whereabouts exposed would be bad news.
128AnonymousNov 5, 2026 00:13
Re: #122
Isn't it your income that leaks? That would be a real problem for wealthy people.
143AnonymousNov 5, 2026 00:21
Re: #122
Most wealthy people file through e-Tax. Here's what a tax return reveals:
・Address
・Name (including family members)
・My Number (including family members)
・Phone number
・Date of birth (including family members)
・Income details — how much they earn and how much tax they pay
・Info on the businesses, employers, rental properties, and securities generating that income

If all that ends up on the dark web….

Background and Key Points of This Story

e-Tax is the online filing system run by the National Tax Agency, and as the push toward electronic filing continues, distribution of paper filing forms is reportedly set to shrink going forward (some users in the thread said the tax office had told them as much directly). Details of the “suspicious communications” cited as the reason for the suspension haven’t been made public, so it’s unclear how much of this reflects an actual intrusion attempt. What came up most in the thread was personal experience of routinely receiving phishing emails impersonating e-Tax, though whether that’s directly tied to this suspension can’t be determined from the information in the article. Concerns were also raised that “if the system were breached, high earners’ addresses and income data could leak” — but that’s speculation based on the kind of information tax returns contain, not a confirmed fact, and no actual data leak has been verified.

*This article is compiled as an excerpt/summary of the 5ch (News Flash+) thread “Suspicious Communications Hit e-Tax, National Tax Agency Suspends Service.”

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