Anthropic proposes a Cyber Jailbreak Severity scale (CJS 0–4) with Amazon, Microsoft, Google

With Claude Fable 5 redeployed globally, Anthropic published more detail on the model's cybersecurity safeguards and proposed a shared industry framework, developed with Amazon, Microsoft and Google under Project Glasswing.

Key points

• A four-tier classifier in Fable 5 blocks prohibited uses (ransomware, wipers, cyber-physical sabotage, defense evasion, malware development/delivery, C2 infrastructure, backbone attacks) while allowing legitimate defensive work (secure coding, patch management, SOC analysis, malware reverse-engineering, incident response) with minimal restrictions.
• The Cyber Jailbreak Severity (CJS) scale runs 0–4, scored on four measures: capability gain, breadth of that gain, ease of weaponisation, and discoverability.
• Summed scores map to bands: CJS-1 Low (1–3.5), CJS-2 Medium (4–6.5), CJS-3 High (7–8.5), CJS-4 Critical (9–10).
• It is a proposed, open framework meant to standardize how vendors and regulators rate the severity of a successful jailbreak.