This weekly roundup covers a massive exposure of personal data from Denmark's national population register, a U.S. bounty on a Chinese hacker accused of stealing COVID-19 research, Japan's plan to actively search for attackers hiding in its critical infrastructure, a pair of breaches at Japanese publisher Nikkei, a call for AI-driven decision-making in security operations, and a Massachusetts town's ongoing recovery from an August cyberattack.  Two threads run through this week's stories. First, attackers keep getting in through doors that were already open: a company's lawful access to a government register, employees' hijacked email accounts, and unpatched mail servers. Second, the time between intrusion and discovery remains dangerously long, which is why governments and security leaders are pushing to find intruders sooner and respond faster. 

The Cyber Express Weekly Roundup 

Hackers Abuse Company's Legitimate Access to Expose Data of 8.8 Million in Denmark 

The Danish government said unauthorized individuals obtained the names, addresses, and CPR numbers of roughly 8.8 million people from the Central Person Register. They did it by misusing the legal access granted to a private Danish company. The register holds records on about 11 million people, including residents, Danes living abroad, and deceased individuals. Read more… 

US Offers $10 Million Reward for Chinese Hacker Accused of Stealing COVID-19 Research 

The U.S. State Department is offering up to $10 million for information on Zhang Yu, a Chinese national accused of hacking COVID-19 research at U.S. universities on behalf of China's Ministry of State Security. Zhang and his alleged partner, Xu Zewei, are also tied to the 2021 HAFNIUM campaign, which exploited Microsoft Exchange vulnerabilities to compromise more than 12,700 U.S. entities. Xu was arrested in Italy in 2025 and extradited to the U.S. in April 2026. Zhang remains at large. Read more… 

Japan to Launch Threat Hunting Program to Find Hidden Attackers in Critical Infrastructure 

Japan plans to partner with private companies in fiscal 2027 to proactively look for attackers who may already be sitting undetected inside power, telecom, and other critical infrastructure networks. The National Cybersecurity Office will build detection methods by recreating attack scenarios in a virtual environment and will share them with operators. The Defense Ministry will provide experienced personnel to companies on request. Read more… 

Nikkei Hit by Two Breaches as Hijacked Accounts Send 9,000 Malicious Emails 

Japanese publisher Nikkei disclosed on October 4 that attackers had taken over employees' Microsoft 365 accounts. On September 30, they used those accounts to send roughly 9,000 emails with malicious links to staff and external contacts. Nikkei also revealed a separate breach of its Google Workspace accounts, ongoing since late July, that may have exposed the names and email addresses of 1,646 employees and business partners. Read more… 

Agentic AI Turns Cybersecurity Into a Race of Decision Speed 

In an opinion piece, Cyble's Salleh Kodri argues that security teams no longer struggle to see threats. Their problem is "decision latency": the time it takes to turn alerts from many tools into the right action. As AI accelerates attackers' reconnaissance and decision-making, Kodri says defenders should use AI to correlate intelligence and act faster. Read more… 

Andover Confirms Attackers Accessed Town Systems in August Cyberattack 

Officials in Andover, Massachusetts, confirmed that the August 13 cyberattack involved unauthorized access to some town systems. They have not yet determined whether any data was stolen or whether personal information was involved. The town says it paid no ransom. It has hired a law firm and cybersecurity firm Vector3 to investigate, with costs covered by cyber insurance. Read more… 

Weekly Cybersecurity Takeaway 

Several of this week’s incidents started with access that looked legitimate. In Denmark, attackers abused a private company’s authorized connection to the national register instead of breaking in. At Nikkei, hijacked employee accounts sent thousands of malicious emails under a trusted name.  Time is the other common thread. Nikkei’s Google Workspace breach ran for over two months before disclosure, and Andover still doesn’t know what was taken. Japan’s threat hunting plan assumes attackers may already be inside, and Kodri warns that spotting an alert means little if acting on it takes too long.  Organizations should monitor third-party access as closely as their own staff’s. They should secure email accounts with phishing-resistant authentication and actively hunt for intruders rather than wait for alerts. 

The U.S. Justice Department and FBI have seized two hacking tools, Microscan and FishHub, that court documents say were operated and used by Flax Typhoon actors working for a China-based company. According to the government, the tools were used to scan, and in some cases hack, U.S. and foreign critical infrastructure systems and other networks. The court-authorized seizures were announced alongside court documents unsealed in the Western District of Pennsylvania. Prosecutors allege the actors worked for Integrity Technology Group (Integrity Tech), a company based in the People's Republic of China (PRC) that holds contracts with the PRC government. The action is the latest step by U.S. authorities against China state-sponsored hackers.

How Flax Typhoon Actors Used Microscan for Vulnerability Scanning

According to court documents, Integrity Tech built and used a botnet of internet-of-things devices infected with a variant of Mirai malware. The botnet supported the company's vulnerability scanning through Microscan, a tool Integrity Tech developed to perform reconnaissance on victim networks and identify weaknesses its clients would later exploit. Targets of Microscan scanning included a U.S. power company based in South Carolina, a multinational non-governmental organization, airports in Japan and Poland, Taiwanese critical infrastructure companies in the natural gas and power sectors, and two Taiwanese universities. Integrity Tech accessed Microscan through c0cc[.]cc, one of the seized domains.

FishHub and the Flax Typhoon Spear Phishing Operation

The second tool, FishHub, allegedly helped compromise computer networks through spear phishing. After gaining initial access, FishHub downloaded additional malware to the victim network. That malware either gave Integrity Tech's clients unauthorized remote access or searched for specific files and sent them to servers controlled by Integrity Tech. Confirmed FishHub victims included about 20 Taiwanese universities. Five seized domains helped deliver the malware: 98aicai[.]com, 98aicode[.]com, outlook3650[.]com, youtubecard[.]com, and linkedinns[.]net.

What Officials Said About Flax Typhoon

Assistant Attorney General for National Security John A. Eisenberg said the United States "will not allow China or its proxies to operate against United States interests with impunity in cyberspace." He added that the National Security Division would continue working to disrupt the Flax Typhoon threats and dismantle the infrastructure sustaining them. Assistant Director Brett Leatherman of the FBI's Cyber Division said, "The PRC relies on contractor and enabling companies to expand the reach and scale of its malicious cyber activity. By exposing and disrupting these enablers, we make it harder for the PRC to target American networks and infrastructure." U.S. Attorney Troy Rivetti for the Western District of Pennsylvania described the seizures as the second disruption of Integrity Tech's operations in as many years. Special Agent in Charge Mark Remily of the FBI San Diego Field Office said the action reflects the FBI's commitment to disrupting PRC state-sponsored cyber actors who threaten critical infrastructure and national security.

Second Disruption of Flax Typhoon Infrastructure

This is the Justice Department's second public technical disruption of Integrity Tech's hacking infrastructure. In September 2024, the department announced the court-authorized disruption of Integrity Tech's Mirai botnet, which included more than 200,000 consumer devices in the United States and worldwide. Alongside the latest seizures, the FBI and other U.S. and foreign partner agencies published a cybersecurity advisory listing indicators of compromise tied to Integrity Tech intrusion activity. The advisory is intended to help network defenders identify and respond to the group's malicious activity. The FBI San Diego and Baltimore Field Offices are investigating the case in coordination with the FBI's Cyber Division. Assistant U.S. Attorney Brendan McKenna for the Western District of Pennsylvania and Trial Attorney Jacques Singer-Emery of the National Security Division's National Security Cyber Section are prosecuting the case. Assistant U.S. Attorney Thomas Sullivan for the District of Maryland and the National Police Agency of Japan provided substantial assistance.

A North Korean cyber actor group known as WaterPlum, also referred to as "Contagious Interview," has infected at least 30,000 devices across more than 100 countries. The group has been stealing cryptocurrency from IT professionals worldwide. A joint advisory was issued on September 18, 2026, by Japan's National Police Agency and National Cybersecurity Office, the US FBI and Department of Defense Cyber Crime Center, Australia's Signals Directorate, and Germany's Federal Intelligence Service and Federal Office for the Protection of the Constitution.

How WaterPlum Hackers Operate

The agencies assess that WaterPlum actors and certain North Korean IT workers operate under the 313 General Bureau of the Munitions Industry Department, part of the Workers' Party of Korea's Central Committee. The group poses as prospective employers, targeting software developers and IT professionals by impersonating artificial intelligence, cryptocurrency, or non-fungible token companies, and by using recruiting services. During fake technical interviews, victims are instructed to download files to complete coding assignments or fix errors on video calls. These files carry malicious Node Package Manager packages embedded with BeaverTail malware, InvisibleFerret, OtterCookie, OtterCandy, or StoatWaffle. Once installed, the malware grants backdoor access, allowing Remote Access Trojans to maintain persistence while infostealers exfiltrate wallet credentials, browser passwords, clipboard data, keystrokes, and identification documents to command-and-control servers.

Scale of the Cryptocurrency Theft

Between December 2025 and July 2026, WaterPlum exfiltrated funds or credentials from over 7,000 cryptocurrency wallets, transferring 1.7 billion Japanese yen, equivalent to 10.71 million USD, to North Korea. Primary targets included web designers, engineers, and specialists in blockchain and Web3 technologies.

Role of Laptop Farms

The advisory also details how North Korean IT workers generate foreign currency through "laptop farms," locations, often an enabler's residence, where employment computers are remotely controlled by workers based in North Korea, China, Russia, and occasionally Africa or Southeast Asia. Enablers supply identification images, bank accounts, and internet connections, then forward payments to the workers after taking a cut. Japanese authorities dismantled a laptop farm for the first time domestically, uncovering evidence of several hundred million yen transferred abroad in cryptocurrency. A related case involved a suspected North Korean applicant at a Japanese cryptocurrency exchange in May 2025, who submitted a forged resume, accessed the recruitment portal via VPN, and displayed mismatched language skills during a video interview. The company declined to hire the applicant, and no damage occurred.

Warning Signs and Recommended Countermeasures

The agencies list red flags including refusal of in-person meetings, requests for cryptocurrency payment, background voices during calls, and repeated video freezes. Recommended defenses include avoiding execution of untrusted code outside a sandbox, treating VSCode projects with caution using "Restricted Mode," deploying Endpoint Detection and Response tools, and immediately disconnecting compromised devices from the internet. Victims are advised to assume wallet data has been exposed, create new wallets on separate devices, and perform full operating system resets.

International Cooperation Continues

The FBI stated it continues to prosecute US-based facilitators who assist North Korean IT workers, while Japanese and American authorities pledged ongoing cooperation to expose revenue-generation schemes benefiting the Kim regime. The advisory noted that WaterPlum and North Korean IT worker operations shared overlapping IP addresses across laptop farms, crowdsourcing platforms, and job applications, indicating coordinated infrastructure. Companies and individual IT professionals are urged to review the tactics outlined in the advisory and strengthen hiring verification processes to prevent further infiltration.

The Liquid Network security incident has taken an unusual turn after the unidentified actors behind the theft of nearly 4,000 BTC offered to return “most” of the funds — but only after the vulnerability that enabled the exploit is fixed across the network.  The purported white-hat hackers communicated their condition through an ongoing exchange with Blockstream, according to Galaxy Research head Alex Thorn. The incident involved roughly $320 million worth of BTC and has raised questions over whether the attackers are genuine security researchers or simply exploiting the language and behavior associated with white-hat hacking.  The episode began on Sunday, when approximately 4,000 BTC was withdrawn from the Liquid Federation wallet. The amount represented about 95% of the Bitcoin that had been pegged into the Liquid sidechain.  Following the withdrawals, Liquid disabled its bridge nodes and paused the network. The stolen funds were subsequently consolidated into a Bitcoin address containing a message that read: “we are whitehats. contact us on chain.”  Liquid, however, has continued to describe the individuals involved as purported white-hat hackers, reflecting the uncertainty surrounding their identity and intentions. 

Liquid Network Security Incident Sparks On-Chain Conversation 

The unusual communication between the attackers and Blockstream has taken place through Bitcoin OP_RETURN messages and PGP-encrypted text.  Thorn reconstructed the exchange and reported that Blockstream attempted to contact the actors at Bitcoin block 965,822. The company sent 1,000 satoshis along with an OP_RETURN message intended to alert its security team and establish a communication channel.  A later transaction included encrypted material addressed to the holder of the relevant key, along with a PGP signature. According to Thorn, the signature could be verified against Blockstream’s published public key, providing an indication that the communication was connected to the company.  The purported white-hat hackers subsequently responded at block 965,869. They moved their own balance and sent 1,000 satoshis to the federation’s peg wallet. Alongside the transaction, they asked whether returning “most” of the withdrawn BTC to the federation address would be acceptable.  That proposal came with a significant condition: the vulnerability responsible for the Liquid Network security incident would have to be fixed first.  “Please fix the bug first,” the hackers told Blockstream. 

White-Hat Hackers Leave Questions Over Returned BTC 

The use of the word “most” has introduced another layer of uncertainty. The message does not specify how much BTC the actors would ultimately return, leaving open the possibility that they could retain a portion of the nearly 4,000 BTC taken from the federation wallet.  There is also no guarantee that the promised return will actually occur. Until the funds move back to the federation-controlled address, almost all of the Bitcoin remains under the control of the unidentified actors.  The incident initially prompted skepticism from Ledger Chief Technology Officer Charles Guillemet, who argued that conventional white-hat hackers generally do not drain hundreds of millions of dollars from a bridge.  Guillemet compared the situation with major cryptocurrency exploits such as Ronin and Euler, where attackers were responsible for substantial losses. His initial assessment suggested that the scale and method of the Liquid incident were inconsistent with the typical behavior expected from legitimate security researchers.  His position later softened after the hackers attempted to communicate with Blockstream. 

BTC Remains Under Hackers’ Control 

Guillemet noted that criminal groups do not typically make efforts to establish direct communication with their victims after carrying out an exploit. The willingness of the actors to communicate therefore created some hope that the funds could eventually be recovered.  “There’s hope,” Guillemet wrote.  He also argued that the vulnerability could potentially be researched using powerful AI systems to identify the underlying flaw without relying on proper disclosure procedures.  For now, however, the outcome of the Liquid Network security incident remains unresolved. The hackers have indicated that they are prepared to return “most” of the BTC, but only once the underlying bug has been fixed across the network.  The development leaves Blockstream and Liquid facing two immediate challenges: addressing the vulnerability that allowed the exploit and determining whether the unidentified actors will honor their commitment.  Until those steps are completed, the nearly 4,000 BTC involved in the incident remains largely outside the federation’s control. The on-chain messages provide a rare window into negotiations between an exploited crypto network and the people claiming responsibility, but they do not yet establish whether the purported white-hat hackers will ultimately return the funds.