'Trusted access for the next era of cyber defense': OpenAI reveals its Mythos rival, designed for cybersecurity pros to spot the next level of attacks

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OpenAI is releasing GPT-5.4-Cyber and teases even better models down the line

A laptop on a red and blue background showing ChatGPT running the GPT-4o model
(Image credit: Future / OpenAI)
  • OpenAI launches GPT‑5.4‑Cyber, a cyber‑defense variant of GPT‑5.4
  • Model adds reverse engineering and lower refusal boundaries for defenders
  • Available via Trusted Access for Cyber program, scaled to thousands of verified users

The AI-powered cybersecurity race has reached a new level after OpenAI announced a new model to rival Anthropic Mythos.

The company revealed the launch of GPT-5.4-Cyber, a modified version of the GPT-5.4 model designed for cybersecurity defense operations.

The main difference is lower refusal boundaries for legitimate cybersecurity tasks, which OpenAI describes as the tool being more “cyber-permissive.” The model now comes with binary reverse engineering capabilities, allowing analysts to hunt for malicious code in programs and apps.

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TIered system and new announcements

OpenAI is seemingly trying to frame Mythos’ limited access as a disadvantage, promising a more “democratized” solution instead - and while GPT-5.4-Cyber will be more open than Mythos, it still won’t be available to anyone.

The tool will still only be available to members of the Trusted Access for Cyber (TAC) program, but OpenAI said it is now scaling it to “thousands of verified individual defenders and hundreds of teams responsible for defending critical software."

The program will now have a tiered verification system, with the highest tier unlocking GPT-5.4-Cyber. Those interested in partaking in TAC can go to chatgpt.com/cyber, while enterprises are advised to reach out to their OpenAI representative. Those who are already part of the program can apply for higher tiers, as well.

OpenAI also said the release is in preparation of an even more capable AI model, due later this year. “In preparation for increasingly more capable models from OpenAI over the next few months, we are fine-tuning our models specifically to enable defensive cybersecurity use cases, starting today with a variant of GPT‑5.4 trained to be cyber-permissive: GPT‑5.4‑Cyber,” the announcement said.

Mythos is an AI model allegedly so powerful that Antrhopic only gave it to a handful of the biggest software companies, such as Microsoft, Apple, and Google. The tool, they claim, was able to find decades-old vulnerabilities with ease which could, in the wrong hands, be catastrophic.

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Sead Fadilpašić

Sead is a seasoned freelance journalist based in Sarajevo, Bosnia and Herzegovina. He writes about IT (cloud, IoT, 5G, VPN) and cybersecurity (ransomware, data breaches, laws and regulations). In his career, spanning more than a decade, he’s written for numerous media outlets, including Al Jazeera Balkans. He’s also held several modules on content writing for Represent Communications.

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