Bruce Schneier:

Medieval Encrypted Letter Decoded
Sent by a Spanish diplomat. Apparently people have been working on it since it was rediscovered in 1860.

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Bruce Schneier:

What Anthropic’s Mythos Means for the Future of Cybersecurity
Two weeks ago, Anthropic announced that its new model, Claude Mythos Preview, can autonomously find and weaponize software vulnerabilities, turning them into working exploits without expert guidance. These were vulnerabilities in key software like operating systems and internet infrastructure that thousands of software developers working on those systems failed to find. This capability will have major security implications, compromising the devices and services we use every day. As a result, Anthropic is not releasing the model to the general public, but instead to a limited number of companies.The news rocked the internet security community. There were few details in Anthropic’s announcement, angering many observers. Some speculate that Anthropic doesn’t have the GPUs to run the thing, and that cybersecurity was the excuse to limit its release. Others argue Anthropic is holding to its AI safety mission. There’s hype and counterhype, reality and marketing. It’s a lot to sort out, even if you’re an expert.We see Mythos as a real but incremental step, one in a long line of incremental steps. But even incremental steps can be important when we look at the big picture.How AI Is Changing CybersecurityWe’ve written about shifting baseline syndrome, a phenomenon that leads people—the public and experts alike—to discount massive long-term changes that are hidden in incremental steps. It has happened with online privacy, and it’s happening with AI. Even if the vulnerabilities found by Mythos could have been found using AI models from last month or last year, they couldn’t have been found by AI models from five years ago.The Mythos announcement reminds us that AI has come a long way in just a few years: The baseline really has shifted. Finding vulnerabilities in source code is the type of task that today’s large language models excel at. Regardless of whether it happened last year or will happen next year, it’s been clear for a while this kind of capability was coming soon. The question is how we adapt to it.We don’t believe that an AI that can hack autonomously will create permanent asymmetry between offense and defense; it’s likely to be more nuanced than that. Some vulnerabilities can be found, verified, and patched automatically. Some vulnerabilities will be hard to find but easy to verify and patch—consider generic cloud-hosted web applications built on standard software stacks, where updates can be deployed quickly. Still others will be easy to find (even without powerful AI) and relatively easy to verify, but harder or impossible to patch, such as IoT appliances and industrial equipment that are rarely updated or can’t be easily modified.Then there are systems whose vulnerabilities will be easy to find in code but difficult to verify in practice. For example, complex distributed systems and cloud platforms can be composed of thousands of interacting services running in parallel, making it difficult to distinguish real vulnerabilities from false positives and to reliably reproduce them.So we must separate the patchable from the unpatchable, and the easy to verify from the hard to verify. This taxonomy also provides us guidance for how to protect such systems in an era of powerful AI vulnerability-finding tools.Unpatchable or hard to verify systems should be protected by wrapping them in more restrictive, tightly controlled layers. You want your fridge or thermostat or industrial control system behind a restrictive and constantly updated firewall, not freely talking to the internet.Distributed systems that are fundamentally interconnected should be traceable and should follow the principle of least privilege, where each component has only the access it needs. These are bog-standard security ideas that we might have been tempted to throw out in the era of AI, but they’re still as relevant as ever.Rethinking Software Security PracticesThis also raises the salience of best practices in software engineering.…

Bruce Schneier:

Claude Mythos Has Found 271 Zero-Days in Firefox
That’s a lot. No, it’s an extraordinary number:Since February, the Firefox team has been working around the clock using frontier AI models to find and fix latent security vulnerabilities in the browser. We wrote previously about our collaboration with Anthropic to scan Firefox with Opus 4.6, which led to fixes for 22 security-sensitive bugs in Firefox 148.As part of our continued collaboration with Anthropic, we had the opportunity to apply an early version of Claude Mythos Preview to Firefox. This week’s release of Firefox 150 includes fixes for 271 vulnerabilities identified during this initial evaluation.As these capabilities reach the hands of more defenders, many other teams are now experiencing the same vertigo we did when the findings first came into focus. For a hardened target, just one such bug would have been red-alert in 2025, and so many at once makes you stop to wonder whether it’s even possible to keep up.Our experience is a hopeful one for teams who shake off the vertigo and get to work. You may need to reprioritize everything else to bring relentless and single-minded focus to the task, but there is light at the end of the tunnel. We are extremely proud of how our team rose to meet this challenge, and others will too. Our work isn’t finished, but we’ve turned the corner and can glimpse a future much better than just keeping up. Defenders finally have a chance to win, decisively.They’re right. Assuming the defenders can patch, and push those patches out to users quickly, this technology favors the defenders.News article.

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Bruce Schneier:

Fast16 Malware
Researchers have reverse-engineered a piece of malware named Fast16. It’s almost certainly state-sponsored, probably US in origin, and was deployed against Iran years before Stuxnet:“…the Fast16 malware was designed to carry out the most subtle form of sabotage ever seen in an in-the-wild malware tool: By automatically spreading across networks and then silently manipulating computation processes in certain software applications that perform high-precision mathematical calculations and simulate physical phenomena, Fast16 can alter the results of those programs to cause failures that range from faulty research results to catastrophic damage to real-world equipment.”Another news article.Lots of interesting details at the links.

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Bruce Schneier:

A Ransomware Negotiator Was Working for a Ransomware Gang
Someone pleaded guilty to secretly working for a ransomware gang as he negotiated ransomware payments for clients.

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Bruce Schneier:

Hacking Polymarket
Polymarket is a platform where people can bet on real-world events, political and otherwise. Leaving the ethical considerations of this aside (for one, it facilitates assassination), one of the issues with making this work is the verification of these real-world events. Polymarket gamblers have threatened a journalist because his story was being used to verify an event. And now, gamblers are taking hair dryers to weather sensors to rig weather bets.There’s also insider trading: a lot of it.

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Bruce Schneier:

DarkSword Malware
DarkSword is a sophisticated piece of malware—probably government designed—that targets iOS.Google Threat Intelligence Group (GTIG) has identified a new iOS full-chain exploit that leveraged multiple zero-day vulnerabilities to fully compromise devices. Based on toolmarks in recovered payloads, we believe the exploit chain to be called DarkSword. Since at least November 2025, GTIG has observed multiple commercial surveillance vendors and suspected state-sponsored actors utilizing DarkSword in distinct campaigns. These threat actors have deployed the exploit chain against targets in Saudi Arabia, Turkey, Malaysia, and Ukraine.DarkSword supports iOS versions 18.4 through 18.7 and utilizes six different vulnerabilities to deploy final-stage payloads. GTIG has identified three distinct malware families deployed following a successful DarkSword compromise: GHOSTBLADE, GHOSTKNIFE, and GHOSTSABER. The proliferation of this single exploit chain across disparate threat actors mirrors the previously discovered Coruna iOS exploit kit. Notably, UNC6353, a suspected Russian espionage group previously observed using Coruna, has recently incorporated DarkSword into their watering hole campaigns.A week after it was identified, a version of it leaked onto the internet, where it is being used more broadly.This news is a month old. Your devices are safe, assuming you patch regularly.

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Bruce Schneier:

Rowhammer Attack Against NVIDIA Chips
A new rowhammer attack gives complete control of NVIDIA CPUs.On Thursday, two research teams, working independently of each other, demonstrated attacks against two cards from Nvidia’s Ampere generation that take GPU rowhammering into new—­and potentially much more consequential—­territory: GDDR bitflips that give adversaries full control of CPU memory, resulting in full system compromise of the host machine. For the attack to work, IOMMU memory management must be disabled, as is the default in BIOS settings.“Our work shows that Rowhammer, which is well-studied on CPUs, is a serious threat on GPUs as well,” said Andrew Kwong, co-author of one of the papers. “GDDRHammer: Greatly Disturbing DRAM Rows­Cross-Component Rowhammer Attacks from Modern GPUs.” “With our work, we… show how an attacker can induce bit flips on the GPU to gain arbitrary read/write access to all of the CPU’s memory, resulting in complete compromise of the machine.”Update Friday, April 3: On Friday, researchers unveiled a third Rowhammer attack that also demonstrates Rowhammer attacks on the RTX A6000 that achieves privilege escalation to a root shell. Unlike the previous two, the researchers said, it works even when IOMMU is enabled.The second paper is GeForge: Hammering GDDR Memory to Forge GPU Page Tables for Fun and Profit:…does largely the same thing, except that instead of exploiting the last-level page table, as GDDRHammer does, it manipulates the last-level page directory. It was able to induce 1,171 bitflips against the RTX 3060 and 202 bitflips against the RTX 6000.GeForge, too, uses novel hammering patterns and memory massaging to corrupt GPU page table mappings in GDDR6 memory to acquire read and write access to the GPU memory space. From there, it acquires the same privileges over host CPU memory. The GeForge proof-of-concept exploit against the RTX 3060 concludes by opening a root shell window that allows the attacker to issue commands that run unfettered privileges on the host machine. The researchers said that both GDDRHammer and GeForge could do the same thing against the RTC 6000.

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Bruce Schneier:

Smart Glasses for the Authorities
ICE is developing its own version of smart glasses, with facial recognition tied to various databases.

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Bruce Schneier:

Insider Betting on Polymarket
Insider trading is rife on Polymarket:Analysis by the Anti-Corruption Data Collective, a non-profit research and advocacy group, found that long-shot bets—­defined as wagers of $2,500 or more at odds of 35 percent or less—­on the platform had an average win rate of around 52 percent in markets on military and defense actions.That compares with a win rate of 25 percent across all politics-focused markets and just 14 percent for all markets on the platform as a whole.It is absolutely insane that this is legal. We already know how insider betting warps sports. Insider betting warping politics—and military actions—is orders of magnitude worse.

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Bruce Schneier:

Friday Squid Blogging: Giant Squid Live in the Waters of Western Australia
Evidence of them has been found by analyzing DNA in the seawater.As usual, you can also use this squid post to talk about the security stories in the news that I haven’t covered.Blog moderation policy.

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Bruce Schneier:

LLMs and Text-in-Text Steganography
Turns out that LLMs are really good at hiding text messages in other text messages.

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Bruce Schneier:

Copy.Fail Linux Vulnerability
This is the worst Linux vulnerability in years.TL;DRcopy.fail is a Linux kernel local privilege escalation, not a browser or clipboard attack. Disclosed by Theori on 29 April 2026 with a working PoC.It abuses the kernel crypto API (AF_ALG sockets) plus splice() to write four bytes at a time straight into the page cache of a file the attacker does not own.The exploit works unmodified across Ubuntu, RHEL, Debian, SUSE, Amazon Linux, Fedora and most others. No race condition, no per-distro offsets.The file on disk is never modified. AIDE, Tripwire and checksum-based monitoring see nothing.Kubernetes Pod Security Standards (Restricted) and the default RuntimeDefault seccomp profile do not block the syscall used. A custom seccomp profile is needed.The mainline fix landed on 1 April. Distros are rolling kernels out now. Patch.“Local privilege escalation” sounds dry, so let me unpack it. It means: an attacker who already has some way to run code on the machine, even as the most boring unprivileged user, can promote themselves to root. From there they can read every file, install backdoors, watch every process, and pivot to other systems.Why does that matter on shared infrastructure? Because “local” covers a lot of ground in 2026: every container on a shared Kubernetes node, every tenant on a shared hosting box, every CI/CD job that runs untrusted pull-request code, every WSL2 instance on a Windows laptop, every containerised AI agent given shell access. They all share one Linux kernel with their neighbours. A kernel LPE collapses that boundary.News article.

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Bruce Schneier:

OpenAI’s GPT-5.5 is as Good as Mythos at Finding Security Vulnerabilities
The UK’s AI Security Institute evaluated GPT-5.5’s ability to find security vulnerabilities, and found that it is comparable to Claude Mythos. Note that the OpenAI model is generally available.Here is the Institute’s evaluation of Mythos.And here is an analysis of a smaller, cheaper model. It requires more scaffolding from the prompter, but it is also just as good.

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Bruce Schneier:

How Dangerous Is Anthropic’s Mythos AI?
Last month, Anthropic made a remarkable announcement about its new model, Claude Mythos Preview: it was so good at finding security vulnerabilities in software that the company would not release it to the general public. Instead, it would only be available to a select group of companies to scan and fix their own software.The announcement requires context—but it contained an essential truth.While Anthropic’s model is really good at finding software vulnerabilities, so are other models. The UK’s AI Security Institute found that OpenAI’s GPT-5.5, already generally available, is comparable in capability. The company Aisle reproduced Anthropic’s published results with smaller, cheaper models.At the same time, Anthropic’s refusal to publicly release its new model makes a virtue out of necessity. Mythos is very expensive to run, and the company doesn’t appear to have the resources for a general release. What better way to juice the company’s valuation than to hint at capabilities but not prove them, and then have others parrot their claims?Nonetheless, the truth is scary. Modern generative AI systems—not just Anthropic’s, but OpenAI’s and other, open-source models—are getting really good at finding and exploiting vulnerabilities in software. And that has important ramifications for cybersecurity: on both the offense and the defense.Attackers will use these capabilities to find, and automatically hack, vulnerabilities in systems of all kinds. They will be able to break into critical systems around the world, sometimes to plant ransomware and make money, sometimes to steal data for espionage purposes, and sometimes to control systems in times of hostility. This will make the world a much more dangerous, and more volatile, place.But at the same time, defenders will use these same capabilities to find, and then patch, many of those same systems. For example, Mozilla used Mythos to find 271 vulnerabilities in Firefox. Those vulnerabilities have been fixed, and will never again be available to attackers. In the future, AIs automatically finding and fixing vulnerabilities in all software will be a normal part of the development process, which will result in much more secure software.Of course, it’s not that simple. We should expect a deluge of both attackers using newly found vulnerabilities to break into systems, and at the same time much more frequent software updates for every app and device we use. But lots of systems aren’t patchable, and many systems that are don’t get patched, meaning that many vulnerabilities will stick around. And it does seem that finding and exploiting is easier than finding and fixing. All of this points to a more dangerous short-term future. Organizations will need to adapt their security to this new reality.But it’s the long term that we need to focus on. Mythos isn’t unique, but it’s more capable than many models that have come before. And it’s less capable than models that will come after. AIs are much better at writing software than they were just six months ago. There’s every reason to believe that they will continue to get better, which means that they will get better at writing more secure software. The endgame gives AI-enhanced defenders advantages over AI-enhanced attackers.Even more interesting are the broader implications. The same searching, pattern-matching and reasoning capabilities that make these models so good at analyzing software almost certainly apply to similar systems. The tax code isn’t computer code, but it’s a series of algorithms with inputs and outputs. It has vulnerabilities; we call them tax loopholes. It has exploits; we call them tax avoidance strategies. And it has black hat hackers: attorneys and accountants.Just as these models are finding hundreds of vulnerabilities in complex software systems, we should expect them to be equally effective at finding many new and undiscovered tax loopholes. I am confident that the major investment banks are working on this right now…

Bruce Schneier:

Upcoming Speaking Engagements
This is a current list of where and when I am scheduled to speak:I’m giving a virtual talk on “The Security of Trust in the Age of AI,” hosted by the Financial Women’s Association of New York, at 6:00 PM ET on May 21, 2026.I’m speaking at the Potsdam Conference on National Cybersecurity at the Hasso Plattner Institut in Potsdam, Germany. The event runs June 24–25, 2026, and my talk will be the evening of June 24.I’m speaking at the Digital Humanism Conference in Vienna, Austria, on Tuesday, June 26, 2026.I’m speaking at the Nuremberg Digital Festival in Nuremburg, Germany, on Wednesday, July 1, 2026.The list is maintained on this page.

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Bruce Schneier:

Bypassing On-Camera Age-Verification Checks
Some AI-based video age-verification checks can be fooled with a fake mustache.

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Bruce Schneier:

Friday Squid Blogging: Bigfin Squid
Article about the bigfin squid.As usual, you can also use this squid post to talk about the security stories in the news that I haven’t covered.Blog moderation policy.

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Bruce Schneier:

Zero-Day Exploit Against Windows BitLocker
It’s nasty, but it requires physical access to the computer:The exploit, named YellowKey, was published earlier this week by a researcher who goes by the alias Nightmare-Eclipse. It reliably bypasses default Windows 11 deployments of BitLocker, the full-volume encryption protection Microsoft provides to make disk contents off-limits to anyone without the decryption key, which is stored in a secured piece of hardware known as a trusted platform module (TPM). BitLocker is a mandatory protection for many organizations, including those that contract with governments.Slashdot thread. And here’s Nightmare-Eclipse’s GitHub account.

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Bruce Schneier:

Laurie Anderson Is Quoting Me
Not by name, but Laurie Anderson quotes me in one of the tracks of her new album:My favorite quote is from a cryptologist who said “If you think technology will solve your problems, you don’t understand technology and you don’t understand your problems.”Also in interviews:“Of course, it’s ridiculous, outrageous, blah, blah, blah,” Anderson says about the ad. ‘But, I mean, my favorite quote on this is from a cryptologist who said, ‘If you think technology will solve your problems, you don’t understand technology ­ and you don’t understand your problems.’ And I think I’m completely on board with that.”People are telling me that she has been reciting this quote in performances for years. (I lost track of her since college and her 1981 hit “”https://www.youtube.com/watch?v=Vkfpi2H8tOE”>O Superman.”)The origins of the quote is from Roger Needham:If you think cryptography can solve your problem, you don’t understand your problem and you don’t understand cryptography.I modified the quote in the preface to my 2000 book Secrets and Lies:A few years ago I heard a quotation, and I am going to modify it here: If you think technology can solve your security problems, then you don’t understand the problems and you don’t understand the technology.I can’t tell you why me in 2000 didn’t credit Needham by name. I should have.I have used the quote pretty consistently since then. Somewhere along the line I dropped “security” from the phrase, and now say it more like Anderson quotes me:If you think technology will solve your problem, you don’t understand your problem and you don’t understand technology.I sometimes use singular and sometimes use plural. Sometimes I say “the problem” and “the technology.” But I think the quote flows better ending with just the word “technology.”

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Bruce Schneier:

On AI Security
Good report:Executive Summary: Let’s say you wanted to make sure that your AI is secure. Can you just maximize the security and privacy benchmark and call it a day? Nope, because benchmarks don’t actually work for measuring AI capabilities (even when they are NOT emergent systemic properties like security). So let’s take a step back: how do you measure security in the first place? Good question. Over the last 30 years, security engineering for software evolved from black box penetration testing, through whitebox code analysis and architectural risk analysis to de facto process-driven standards like the Building Security In Maturity Model (BSIMM). Software had a very deep impact on business operations, and it appears that AI is going to have an even deeper impact. Will a software security-like measurement move work for AI? Probably. In the meantime we can make real progress in AI security by cleaning up our WHAT piles and managing risk by identifying and applying good assurance processes. (Spoiler alert: no matter what we do, we still don’t get a security meter for AI, so we need to be extra vigilant about security.)

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