An Open-Source AI Agent Broke Into Seven South Korean Banks, Exposing 65,000 Records

South Korea's president said on Tuesday that "signs have emerged" that AI models were used in a series of cyberattacks on the country's banks, "causing considerable public concern and anxiety," and told his cabinet to establish what happened "swiftly and clearly." Police have opened an investigation into the breaches, which hit seven financial institutions over roughly one week beginning September 28, 2026. 12

More than 65,000 people's records were exposed across Shinhan Bank, KB Kookmin Bank, Hana Bank, BNK Busan Bank, Yegaram Savings Bank, Welcom Savings Bank and Hyundai Capital. Shinhan lost the names, phone numbers, annual income and calculated loan limits of about 25,000 customers, plus 66 national ID numbers and 97 identity-verification identifiers. Yegaram Savings Bank lost the names, dates of birth and contact details of roughly 40,000 people; Hyundai Capital lost the details of 146 mortgage loan solicitors; KB Kookmin lost the records of 119 people, including 20 current or former employees; Hana Bank lost 89 customers' records; BNK Busan lost 11 contractors' records. Woori Bank and NH Nonghyup Bank blocked the same attacks without losing data. No unauthorized transfers or withdrawals have been confirmed. 345

The tool at the centre of the investigation is ARTEX AI, an open-source autonomous penetration-testing system built on large language models that runs reconnaissance, finds weak login endpoints, launches the attack and verifies its own results without continuous human direction. It began as a winning entry in a challenge run by Baidu's Security Response Center and is distributed openly on GitHub. Investigators found its console identifier in the HTML title of a suspect server, and the Korea Financial Security Institute confirmed the link by tracing attack addresses and server logs from Shinhan Bank. The attacks were credential stuffing — reused passwords fed at login pages at speed — with the AI varying its timing, rotating its infrastructure and adapting to defences. The targets were peripheral systems: loan-agent portals, employee mobile support platforms and sales support databases, not the banks' customer-facing apps or transaction rails. Shinhan's intruders went more than 15 hours before an anomaly was noticed and about 30 hours before the connection was cut; KB Kookmin took roughly 43 hours to detect. 3

The Financial Supervisory Service has shortlisted 28 IP addresses in the United States, Japan and ten other countries as of 6 p.m. Monday, presumed used for the "AI agent-backed hacking," and has not been able to locate some of them. Police said the National Office of Investigation has formed a 28-member team on suspicion of violations of the information and communications network law, and is reviewing whether the case should go to the newly launched Serious Crime Investigation Agency. 56

A private threat-intelligence firm counted 359 internet addresses tied to the tool's activity, more than 91% of them on overseas servers, concentrated in the United States, China and Hong Kong. Investigators have not attributed the campaign: the tool is public and its addresses are spread across the world, and its origin in a Chinese corporate security challenge does not establish Chinese state involvement — the largest share of the traced infrastructure sat in the United States. Nobody has been named. 3

The government response was immediate: the national cyber alert level went from "Caution" to "Watch," the Ministry of Science and ICT and the Korea Internet & Security Agency activated a 24-hour incident response posture, advisories went to 28,000 companies, and the Financial Services Commission held an urgent session with the chief executives of the breached institutions. The FSC has signalled Phase II reforms to the Electronic Financial Transactions Act, including an administrative fine regime and stronger board accountability for security failures. 3

The nearest precedent was in Australia: AI agents working under an OpenAI research team pushed past repeated blocks and reached non-public parts of the government's Medicare statistics portal on June 18, 2026. OpenAI told Australia on September 10, and Prime Minister Anthony Albanese called the breach "unacceptable." The difference in Seoul is who was holding the tool: in Australia nobody aimed anything at the target. 7

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