Most people have opened their messages to find a suspicious alert urgently telling them that a package cannot be delivered, a toll remains unpaid, a bank account needs attention, or a tax bill is overdue. The details may change, but the goal is the same: to get someone to click, share personal information, or pay.
These messages are relentless. Delete and block one, and another takes its place. Ignore them, and more will follow. Fall for one, and the floodgates open. What appears to be a simple scam message is often the visible end of a much larger transnational cybercriminal operation.
When Microsoft and Japan’s National Police Agency (NPA) followed a wave of fraud and scam activity targeting people and businesses in Japan, they expected to find individual campaigns. Instead, they found themselves inside a sprawling Chinese-language cybercrime marketplace where criminals could buy accounts, hosting services and tools used to create fake websites and online identities. The investigation expanded globally, involving the Japan Cybercrime Control Center (JC3), Resecurity, Cloudflare, Oracle, Proofpoint and TRM Labs to uncover the businesses sustaining this criminal ecosystem.
Today, Microsoft and Health-ISAC, a global non-profit that helps health sector organizations share cyber threat information and collaborate to improve operational resilience, are moving to dismantle three components of this criminal marketplace: YAM Store, CoGUI and Iron Man.
Since January 2026, YAM Store, CoGUI and Iron Man have collectively enabled more than one billion malicious messages targeting over 75,000 organizations worldwide, including more than 750 million messages geared toward Microsoft customers alone. These messages have been used to target consumers, healthcare organizations, financial institutions, and other businesses in more than 150 countries, generating tens of millions of dollars for their operators.
Tracing the businesses behind the scams
The investigation began in late 2025 after Japan’s NPA alerted Microsoft to malicious messaging campaigns targeting people in Japan. NPA continued providing intelligence and investigative support as the partners traced those campaigns back to the businesses supplying criminals around the world.
The trail led investigators deep into a Chinese-language cybercrime ecosystem that was difficult for non-native-speaking investigators to penetrate. There, they gained access to CoGUI, which supplied criminals with ready-made websites and messages impersonating companies, financial institutions, government agencies, and other trusted organizations. Instead of creating fraudulent websites themselves, criminals could quickly deploy pages designed to steal passwords, payment information, and other personal data.
As Microsoft’s investigation expanded, intelligence from JC3 helped confirm the scale of the activity affecting Japanese organizations and their customers. Drawing on information collected across its network of more than 130 member organizations, JC3 connected what appeared to be separate incidents to a broader pattern of scams targeting Japanese companies and financial institutions, including efforts to defraud consumers and to steal credentials and other sensitive information.
One name that kept appearing throughout the investigation was YAM Store. YAM Store operated much like an online shop. Customers could browse products, compare prices and purchase fraudulent Microsoft and Google accounts and other ready-made tools used to carry out scams, including credential theft. Controlled purchases conducted by Microsoft helped confirm how it worked.
In some cases, operators acquired internet domains that legitimate organizations had allowed to expire, often targeting certain sectors, such as non-profits and education, with specialized product offerings. They then rebuilt the websites to make those organizations appear active, allowing them to fraudulently obtain Microsoft 365 accounts that could later be sold through YAM Store.
Ready-made tools
YAM Store provided criminal infrastructure that was frequently paired with tools and services such as CoGUI. As investigators dug deeper, they found that the marketplace was already evolving. CoGUI had become one of the most widely used offerings in the ecosystem, particularly targeting victims in Japan and the United States but by mid-2026 it was increasingly being replaced by a newer offering known as Iron Man.
Iron Man expanded the model by giving criminals access to thousands of ready-made templates designed to impersonate trusted organizations. Criminals could then quickly deploy email, text and web content tailored to specific brands, industries and countries.
Through test purchases and work with Resecurity, investigators gained access to Iron Man and identified more than 2,300 templates impersonating banks, retailers, healthcare providers, transportation authorities, police departments, government agencies, and other organizations across more than 150 countries worldwide. Some were designed for government impersonation scams, using the appearance of official authority to pressure victims into making payments or disclosing sensitive personal information. Others impersonated organizations across industries, countries, and languages, from banks and airlines to telecommunications companies, retailers, and parcel delivery services.
Examples of these impersonation templates are below. Importantly, the presence of an organization or government entity in these templates does not indicate that its systems were compromised.
A blog from Microsoft Threat Intelligence shares more details on the network, as well as steps customers can take to protect themselves.
Putting the pieces together
No single organization saw the full picture. Japan’s NPA played a critical role throughout the investigation, providing intelligence, investigative support and collaboration that helped uncover how the operation worked. JC3 helped establish the scale of the activity affecting Japanese organizations and consumers. Health-ISAC provided insight into impacts affecting healthcare organizations, while Resecurity, Cloudflare, Oracle, Proofpoint and TRM Labs contributed intelligence and investigative support.
Working together, and with the assistance of AI tools, we connected accounts, websites, and infrastructure that initially appeared unrelated, helping expose the broader criminal marketplace behind them. Microsoft also worked closely and shared intelligence with U.S. Secret Service and international law enforcement partners.
This investigation also reflects a broader trend highlighted in this year’s Microsoft Digital Defense Report: modern fraud increasingly relies on businesses and services that make it easier for criminals to reach more victims. It took two-way information sharing across industries and international borders to uncover how these deeply interconnected services worked together.
Going after the suppliers
With an order from the United States District Court for the Southern District of Florida, Microsoft and Health-ISAC seized and redirected domains that were part of the underlying infrastructure powering YAM Store, CoGUI and Iron Man. Microsoft has already disabled more than 20,000 accounts connected to YAM Store and continues to dismantle the operation by removing infrastructure hosted on its services and blocking more than 100,000 domains used for impersonation and fraud.
What began with scam activity targeting people and organizations in Japan led investigators to an underground service economy supplying criminals around the world. YAM Store, CoGUI and Iron Man are only part of that larger criminal network, but disrupting them makes it harder for criminals to obtain the accounts, tools and infrastructure they rely on.
The scam message is often the only part victims see. The businesses behind it are what make it possible.
Tags: DCU, Microsoft Digital Crimes Unit, The Digital Crimes Unit
