AhnLab, a South Korean cybersecurity firm, issued security guidelines on October 2 after account takeover attacks and data breaches involving Shinhan Bank, KB Kookmin Bank and Hana Bank. The incidents highlight how stolen credentials can trigger credential stuffing campaigns, in which automated tools test reused usernames and passwords across banking, retail, portal and social-network accounts. AhnLab advises consumers to use a separate password for every service, prioritize email-account security and enable multifactor authentication. Users should also avoid links in unsolicited messages offering breach checks, compensation or account protection, and instead access financial services through official apps or directly typed website addresses. Generative AI and advanced scripts have made such attacks more extensive and targeted, while criminals combine information from multiple sources to identify potential victims.