UK Banks Denied Access to Mythos AI Amid Cybersecurity Concerns
Severity: Medium (Score: 58.0)
Sources: Coinfomania, Benzinga, Cryptobriefing, Retailbankerinternational, Theregister
Published: · Updated:
Keywords: banks, mythos, access, bank, still, model, anthropic
Summary
As of May 29, 2026, UK banks still lack access to Anthropic's Mythos AI model, which is crucial for testing cybersecurity defenses. Bank of England Governor Andrew Bailey highlighted that the delay stems from political and licensing issues with the US administration. Meanwhile, OpenAI has offered access to its GPT-5.5-Cyber model to nine UK banks, providing an alternative for cybersecurity testing. The AI Security Institute found both models to perform similarly in simulating cyber-attacks. Concerns persist regarding the potential misuse of Mythos, which has demonstrated advanced capabilities in penetrating corporate networks. The situation reflects a broader challenge in aligning AI access with regulatory frameworks across jurisdictions. The lack of access to Mythos creates a defensive gap for UK banks managing trillions in assets. Key Points: • UK banks remain unable to access Anthropic's Mythos AI model due to political delays. • OpenAI has stepped in, offering access to its GPT-5.5-Cyber model to nine major UK banks. • Concerns about the misuse of Mythos highlight the need for regulatory frameworks in AI deployment.
Detailed Analysis
**Impact** Nine major UK banks, including Lloyds Banking Group, HSBC, Nationwide, NatWest, and Santander, are affected by restricted access to Anthropic’s Mythos AI model, limiting their ability to conduct advanced cyber-attack simulations. This impacts financial institutions managing trillions in assets within the UK and potentially wider European markets. The delay in access creates a defensive blind spot, increasing exposure to sophisticated AI-enabled cyber threats and uneven preparedness compared to banks in other jurisdictions with access to similar tools like OpenAI’s GPT-5.5-Cyber. **Technical Details** Anthropic’s Mythos AI model and OpenAI’s GPT-5.5-Cyber are designed to simulate complex cyber-attacks, including comprehensive corporate network penetration testing that can identify hidden security weaknesses in legacy and modern systems. Mythos demonstrated the ability to thread through layered defenses akin to advanced persistent threats. No specific malware, CVEs, or IOCs are disclosed in the reporting. The primary attack vector simulated involves AI-driven exploitation of vulnerabilities within banking applications and infrastructure, focusing on the reconnaissance and exploitation stages of the kill chain. **Recommended Response** Defenders should prioritize gaining controlled access to advanced AI-driven penetration testing tools, such as OpenAI’s GPT-5.5-Cyber, to simulate and identify vulnerabilities in their systems. Financial institutions must maintain human oversight to validate AI-generated findings and mitigate false positives. Monitoring developments in US and UK policy on AI model access and pre-release engagement frameworks is critical. Organizations should track announcements from Anthropic and other providers regarding sandboxed environments or audit interfaces for red-teaming purposes.
Source articles (19)
- Japan weighs financial system shutdowns over AI cyber risks — Asahi · 2026-05-20
Japan is considering allowing financial institutions to “proactively” suspend their systems at their discretion if they face the risk of cyberattacks leveraging advanced artificial intelligence models… - Japan weighs financial system shutdowns over AI cyber risks — Asahi · 2026-05-21
The logo of Anthropic, the American startup behind Claude Mythos (Reuters file photo) Security guard, 72, behind design of Nike’s new Shinjuku store Video obtained of NuVasive Japan sales rep helping… - Japan Eyes Financial System Shutdown In Mythos Attack — www.nippon.com · 2026-05-26
Tokyo, May 20 (Jiji Press)--A Japanese public-private working group is considering actively shutting down financial systems as an option to deal with possible cyberattacks that utilize Claude Mythos,… - Japan's Top 3 Banks Get OpenAI Access to Fight Cyberattacks — Coinfomania · 2026-05-29
Japan's top three banking giants MUFG, SMBC, and Mizuho adopt OpenAI's newest AI models to strengthen their cybersecurity threat detection. Summary is AI generated, newsroom reviewed. Mitsubishi UFJ,… - Japan's Top Banks Adopt OpenAI AI Model to Counter Cyber Threats — Banklesstimes · 2026-05-29
Since launching 12 years ago, Bankless Times has brought unbiased news and leading comparison in the crypto & financial markets. Our articles and guides are based on high quality, fact checked researc… - Japan's megabanks seek OpenAI model to harden cyber defences — Nationthailand · 2026-05-29
Japan ’s three megabanks are expected to gain access to a new artificial intelligence model from OpenAI, the US company behind the generative AI chatbot ChatGPT , informed sources said on Thursday (Ma… - OpenAI Gives Japan's Biggest Banks A Cybersecurity Weapon - Microsoft (NASDAQ:MSFT) — Benzinga · 2026-05-30
Japan's three largest banks are at the center of this deployment. MUFG Bank, Sumitomo Mitsui Banking, and Mizuho Bank are expected to receive access, Nikkei reported Thursday. OpenAI is delivering the… - OpenAI Grants GPT-5.5 Access to Japan Banks | Let's Data Science — Letsdatascience · 2026-05-30
Japanese Finance Minister Satsuki Katayama said that OpenAI has given some Japanese financial institutions access to its GPT-5.5 model to help guard against cyberattacks, Reuters reported. Katayama ma… - UK banks still lack access to Mythos AI model — Itnews.Au · 2026-05-31
British banks still have not been able to gain access to Anthropic's Mythos artificial intelligence model to check their systems against cyber threats, six weeks after it first drew concern, Bank of… - Bank of England Says UK Banks Lack Mythos Access | Let's Data Science — Letsdatascience · 2026-05-31
Bank of England governor Andrew Bailey told Bloomberg that British banks still have not gained access to Anthropic PBC's Mythos model six weeks after it first drew concern. Bailey said Anthropic was w… - Japan banks get OpenAI GPT — Retailbankerinternational · 2026-06-01
Several Japanese financial groups have been granted access to OpenAI’s GPT-5.5 model for use in cyber defence, Finance Minister Satsuki Katayama said after talks in Tokyo with the company’s chief stra… - UK banks blocked from cyber AI tool Mythos get offer from rival OpenAI — Bbc · 2026-06-01
OpenAI has offered nine major UK banks access to its cyber security AI tool GPT-5.5 Cyber, as its fierce rival Anthropic has blocked them in previews of its version, Claude Mythos. Both tools are desi… - OpenAI offers UK banks access to GPT — Cryptobriefing · 2026-06-01
Nine UK banks get an invitation to test OpenAI's cybersecurity model while Anthropic's more powerful Mythos Preview remains out of reach. The UK’s biggest banks have a cybersecurity AI problem, and Op… - OpenAI opens GPT-5.5 Cyber to British banks amid Mythos access battle — Cybernews · 2026-06-01
OpenAI has offered nine major UK banks access to its cybersecurity-focused GPT-5.5 Cyber model, as lenders remain unable to test their systems using Anthropic’s rival Claude Mythos despite concerns th… - OpenAI gives UK banks access to cybersecurity model — Finextra · 2026-06-02
OpenAI has offered the UK's biggest banks access to its new cybersecurity AI model. The decision contrasts with the approach taken by rival Anthropic, which continues to keep its Mythos model out of t… - OpenAI offers UK banks cyber tool access as Anthropic limits Mythos — Retailbankerinternational · 2026-06-02
OpenAI has made its GPT-5.5 Cyber system available to nine leading UK banks, while competitor Anthropic has not included them in early access to its Claude Mythos model, reported BBC. The two systems… - UK banks gain access to OpenAI cybersecurity tool — Fstech · 2026-06-02
OpenAI has granted nine major UK banks access to its GPT-5.5 Cyber model this week, offering lenders a powerful new cybersecurity tool after rival Anthropic restricted access to its Claude Mythos syst… - UK banks offered access to OpenAI’s GPT-5.5 amid exclusion from Anthropic’s Glasswing expansion — Theregister · 2026-06-03
150 new organizations inducted to cyber’s Soho House, including the first outside the US UK banks are set to receive access to OpenAI’s GPT-5.5 Cyber after being excluded from Anthropic’s latest expan… - Beware the ‘son of Mythos,’ security experts warn — Csoonline · 2026-06-04
LONDON — Enterprise security teams were urged by security experts at Infosecurity Europe to brace for impact as both Anthrophic and OpenAI expand access to their frontier AI models for vulnerability d…
Timeline
- 2026-04-01 — Mythos AI model launched: Anthropic released the Mythos AI model, raising significant cybersecurity concerns.
- 2026-05-29 — UK banks still lack access to Mythos: Bank of England Governor Andrew Bailey confirmed UK banks are still unable to access Mythos due to political hold-ups.
- 2026-05-31 — OpenAI offers access to GPT-5.5-Cyber: OpenAI provided access to its GPT-5.5-Cyber model to nine major UK banks as an alternative to Mythos.
- 2026-05-31 — Bailey discusses Mythos access issues: Governor Bailey emphasized the importance of access to Mythos for testing cybersecurity defenses, citing political delays.
Related entities
- Phishing (Attack Type)
- Ransomware (Attack Type)
- Project Glasswing (Campaign)
- Mitsubishi UFJ Financial Group (Company)
- Mizuho Bank (Company)
- Sumitomo Mitsui Banking Corporation (Company)
- Canada (Country)
- Japan (Country)
- Financial (Industry)
- Claude (Tool)
- Gpt-5.5 Cyber (Tool)
- Mythos (Tool)
- Mythos Preview (Tool)
- Claude Mythos Preview (Platform)
- GPT-5.5-Cyber (Platform)