The Financial Security Institute told bank security officers in mid-September that AI agents were probing Oracle WebLogic servers across the sector, yet customer data still leaked from several lenders within two weeks, according to briefing materials disclosed to lawmakers.
Rep. Han Chang-min of the Rebuilding Korea Party released slides from a September 17 seminar where FSI staff described an attacker instructing an agent built on a Chinese large language model to scan for internet-facing WebLogic instances. The next day, the agent exploited a flaw, planted a web shell, and was stopped before downloading additional malware, the presentation said.
What broke afterward
By early October, Yegaram Savings Bank reported roughly 40,000 customer records exposed and Shinhan Bank about 25,000 entries including names, phone numbers, and income bands. KB Kookmin, Hana, BNK Busan, Welcome Savings Bank, and Hyundai Capital confirmed breaches, while Woori and NH NongHyup said they blocked attempts.
President Lee Jae Myung told a cabinet meeting that signs pointed to AI-assisted intrusions and ordered a probe. The National Office of Investigation opened a case, and CrowdStrike linked open-source ARTEX tooling running on DeepSeek models to follow-on activity.
Supervision gap
FSI presenters urged continuous monitoring, warning that once- or twice-a-year penetration tests would miss agent-driven scans. Several institutions that attended the September briefing were among those hit in October, raising questions about how quickly patches propagated across federated IT stacks.
Card issuers responded with tighter fraud alerts, but the core issue is internet-facing middleware on legacy stacks. Regulators ordered emergency reviews of financial-sector perimeter controls while lawmakers demand timelines for retiring WebLogic versions that no longer receive vendor support.
Customer steps
Affected banks are notifying users through app messages and mailed notices. Customers should rotate passwords, enable two-factor authentication, and treat unsolicited refund texts as bogus messages regardless of bank branding. Prosecutors have not publicly named individual hackers, and institutions emphasize that account passwords were not included in every leak.
Vendor response
Oracle Korea issued a bulletin urging financial clients to apply emergency patches for supported WebLogic builds and to segment management interfaces from the public internet. Several lenders said they are migrating legacy portals to containerized stacks, a multi-year project that cannot outrun automated scanning tools available to criminals.