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Mon, 01 Jun 2026

Mon, 01 Jun 2026 UK banks blocked from cyber AI tool Mythos get offer from rival OpenAI

Nine banks have been offered access to GPT 5.5 Cyber, as fierce rival Anthropic has blocked previews of its tool.
OpenAI has offered nine major UK banks access to its cyber security AI tool, GPT-5.5 Cyber, after rival Anthropic blocked them from using its own version, Claude Mythos, in advance. Both tools are capable of identifying hidden security vulnerabilities in digital systems and outperforming humans at certain hacking and cybersecurity tasks. In April, Anthropic announced Mythos' capabilities, including the discovery of a 30-year-old weakness in a legacy system that had gone undetected. However, some finance ministers, central bankers, and financiers have expressed concerns about the model's potential to compromise financial systems. Following this, OpenAI made its own tool available to the UK banks, which include Lloyds Banking Group, HSBC, and Nationwide, while NatWest and Santander already had access under existing agreements. The AI Security Institute reported that both tools performed similarly in tests set by the institute. According to OpenAI's former UK Chancellor George Osborne, who is now a senior executive at the company, its tool would only be available to those deemed trustworthy. Anthropic, on the other hand, is working to expand access to Mythos while maintaining that it has superior capabilities.