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Not super surprising that Anthropic is shipping a vulnerability detection feature -- OpenAI announced Aardvark back in October (https://openai.com/index/introducing-aardvark/) and Google announced BigSleep in Nov 2024 (https://cloud.google.com/blog/products/identity-security/clo...).

The impact question is really around scale; a few weeks ago Anthropic claimed 500 "high-severity" vulnerabilities discovered by Opus 4.6 (https://red.anthropic.com/2026/zero-days/). There's been some skepticism about whether they are truly high severity, but it's a much larger number than what BigSleep found (~20) and Aardvark hasn't released public numbers.

As someone who founded a company in the space (Semgrep), I really appreciated that the DARPA AIxCC competition required players using LLMs for vulnerability discovery to disclose $cost/vuln and the confusion matrix of false positives along with it. It's clear that LLMs are super valuable for vulnerability discovery, but without that information it's difficult to know which foundation model is really leading.

What we've found is that giving LLM security agents access to good tools (Semgrep, CodeQL, etc.) makes them significantly better esp. when it comes to false positives. We think the future is more "virtual security engineer" agents using tools with humans acting as the appsec manager. Would be very interested to hear from other people on HN who have been trying this approach!

>There's been some skepticism about whether they are truly high severity

To be honest this is an even bigger problem with Semgrep and other SAST tools. Developers just want the .1% of findings that actually lead to issues, but flagging patterns will always lead to huge false positive rates.

I do something similar as what you suggested and it does work well -pattern match + LLM. The downside is this only applies to SAST and so far nobody has found a way to address the findings that make up 90% of a security team's noise, namely SCA and container images.

> What we've found is that giving LLM security agents access to good tools (Semgrep, CodeQL, etc.) makes them significantly better

100% agree - I spun out an internal tool I've been using to close the loop with website audits (more focus on website sec + perf + seo etc. rather than appsec) in agents and the results so far have been remarkable:

https://squirrelscan.com/

Human written rules with an agent step that dynamically updates config to squash false positives (with verification) and find issues while also allowing the llm to reason.

Anakin: I'm going to save the world with my AI vulnerability scanner, Padme.

Padme: You're scanning for vulnerabilities so you can fix them, Anakin?

Anakin: ...

Padme: You're scanning for vulnerabilities so you can FIX THEM, right, Annie?

I assume that's why this is gated behind a request for access from teams / enterprise users rather than being GA

but there are open versions available built on the cn OSS models:

https://github.com/lintsinghua/DeepAudit

The GA functionality is already here with a crafted prompt or jailbreak :)

it's gone a bit unnoticed that they've stopped support for response prefilling in the 4.6 models :/

Definitely will be a fight against bad actors pulling bulk open source software projects, npm packages, etc and running this for their own 0 days.

I hope Anthropic can place alerts for their team to look for accounts with abnormal usage pre-emptively.

You want frontier models to actively prevent people from using them to do vulnerability research because you're worried bad people will do vulnerability research?

Not at all. I was suggesting if an account is performing source code level request scanning of "numerous" codebases - that it could be an account of interest. A sign of mis-use.

This is different than someones "npm audit" suggesting issues with packages in a build and updating to new revisions. Also different than iterating deeply on source code for a project (eg: nginx web server).

I don't understand the joke here.

It's an Internet trope — we could link to knowyourmeme, or link to the HN Guidelines

A vuln scanner is dual-use.

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FWIW Claude Code Opus 4.5 ranks ~71% accuracy on the OpenSSF CVE Benchmark that we ran against DeepSource (https://deepsource.com/benchmarks).

We have a different approach, in that we're using SAST as a fast first pass on the code (also helps ground the agent, more effective than just asking the model to "act like a security researcher"). Then, we're using pre-computer static analysis artifacts about the code (like data flow graphs, control flow graphs, dependency graphs, taint sources/sinks) as "data sources" accessible to the agent when the LLM review kicks in. As a result, we're seeing higher accuracy than others.

Haven't gotten access to this new feature yet, but when we do we'd update our benchmarks.

> "Rather than scanning for known patterns, Claude Code Security reads and reasons about your code the way a human security researcher would: understanding how components interact, tracing how data moves through your application, and catching complex vulnerabilities that rule-based tools miss."

Fascinating! Our team has been blending static code analysis and AI for a while and think it's a clever approach for the security use case the Anthropic team's targeting here.

I hope this is better than their competitors products. So far I've been underwhelmed. They basically just find stuff that's already identified by static analysis tooling and toss in a bunch of false positives from the AI scans.

There's a lot of skepticism in the security world about whether AI agents can "think outside the box" enough to replicate or augment senior-level security engineers.

I don't yet have access to Claude Code Security, but I think that line of reasoning misses the point. Maybe even the real benefit.

Just like architectural thinking is still important when developing software with AI, creative security assessments will probably always be a key component of security evaluation.

But you don't need highly paid security engineers to tell you that you forgot to sanitize input, or you're using a vulnerable component, or to identify any of the myriad issues we currently use "dumb" scanners for.

My hope is that tools like this can help automate away the "busywork" of security. We'll see how well it really works.

LLMs and particularly Claude are very capable security engineers. My startup builds offensive pentesting agents (so more like red teaming), and if you give it a few hours to churn on an endpoint it will find all sorts of wacky things a human won't bother to check.

I am seeing something closer to the opposite of skepticism among vulnerability researchers. It's not my place to name names, but for every Halvar Flake talking publicly about this stuff, there are 4 more people of similar stature talking privately about it.

People use whatever tools are the most effective and they have plenty of incentive not to talk publicly about them. I think the era of openness has passed us by. But why does stature matter anyway? If I look at chromium or MSRC bug reports, scarcely any of the submitters are from Europe/US and certainly don't have anything resembling stature. That guy hasn't done anything of note in the field in a long time from what I know, he's kind of boomer (you too, no disrespect).

Claude Opus 4.6 has been amazing at identifying security vulnerabilities for us. Less than 50% falae positives.

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Limited preview for researchers, who will be hand picked to write positive reviews.

Enough of this frontier grifting. Make it testable for open source developers at no cost and without login or get lost. You won't of course, because you'd get an unfiltered evaluation instead of guerilla marketing via blog posts, secrecy, and name-dropping researchers that cannot be disclosed.

I thought they'd noticed how many of my Claude tokens I've been burning trying to build defences against the AI bot swarms. Sadly not.

Is it only crawlers or bots that abuse your product?

We have been developing our own system (1) for several years, and it's built by engineers, not Claude. Take a look — maybe it could be helpful for your case.

1. https://github.com/tirrenotechnologies/tirreno

Solve a problem and everyone praises you.

No one knows you also caused that problem.