Ending the “silent drop”: how Dynamic Path MTU Discovery makes the Cloudflare One Client more resilient

You’ve likely seen this support ticket countless times: a user’s Internet connection that worked just fine a moment ago for Slack and DNS lookups is suddenly hung the moment they attempt a large file upload, join a video call, or initiate an SSH session. The culprit isn't usually a bandwidth shortage or service outage issue, it is the "PMTUD Black Hole" — a frustration that occurs when packets are too large for a specific network path, but the network fails to communicate that limit back to the sender. This situation often happens when you’re locked into using networks you do not manage or vendors with maximum transmission unit (MTU) restrictions, and you have no means to address the problem.

Today, we are moving past these legacy networking constraints. By implementing Path MTU Discovery (PMTUD), the Cloudflare One Client has shifted from a passive observer to an active participant in path discovery.

Dynamic Path MTU Discovery allows the client to intelligently and dynamically adjust to the optimal packet size for most network paths using MTUs above 1281 bytes. This ensures that a user’s connection remains stable, whether they are on a high-speed corporate backbone or a restrictive cellular network.

The “modern Continue reading

A QUICker SASE client: re-building Proxy Mode

When you need to use a proxy to keep your zero trust environment secure, it often comes with a cost: poor performance for your users. Soon after deploying a client proxy, security teams are generally slammed with support tickets from users frustrated with sluggish browser speed, slow file transfers, and video calls glitching at just the wrong moment. After a while, you start to chalk it up to the proxy — potentially blinding yourself to other issues affecting performance. 

We knew it didn’t have to be this way. We knew users could go faster, without sacrificing security, if we completely re-built our approach to proxy mode. So we did.

In the early days of developing the device client for our SASE platform, Cloudflare One, we prioritized universal compatibility. When an admin enabled proxy mode, the Client acted as a local SOCKS5 or HTTP proxy. However, because our underlying tunnel architecture was built on WireGuard, a Layer 3 (L3) protocol, we faced a technical hurdle: how to get application-layer (L4) TCP traffic into an L3 tunnel. Moving from L4 to L3 was especially difficult because our desktop Client works across multiple platforms (Windows, macOS, Linux) so we couldn’t use Continue reading

How Automatic Return Routing solves IP overlap

The public Internet relies on a fundamental principle of predictable routing: a single IP address points to a logically unique destination. Even in an Anycast architecture like Cloudflare’s, where one IP is announced from hundreds of locations, every instance of that IP represents the same service. The routing table always knows exactly where a packet is intended to go.

This principle holds up because global addressing authorities assign IP space to organizations to prevent duplication or conflict. When everyone adheres to a single, authoritative registry, a routing table functions as a source of absolute truth.

On the public Internet, an IP address is like a unique, globally registered national identity card. In private networks, an IP is just a name like “John Smith”, which is perfectly fine until you have three of them in the same room trying to talk to the same person.

As we expand Cloudflare One to become the connectivity cloud for enterprise backbones, we’ve entered the messy reality of private IP address space. There are good reasons why duplication arises, and enterprises need solutions to handle these conflicts.

Today, we are introducing Automatic Return Routing (ARR) in Closed Beta. ARR is an optional tool for Continue reading

Using Mitmproxy to Observe kubectl Traffic

When I first started learning Kubernetes, I had the idea that observing the network traffic between a client system using kubectl and the Kubernetes API Server would be a useful thing to do. The source of the idea is unclear; I am unsure why I thought this would be useful as a learning tool. Regardless, I continued on with learning Kubernetes and never really pursued this idea—until this week. I found it can be a useful troubleshooting technique, but I will leave it up to you to determine if it is a useful learning technique. In this post, I will show you how to observe kubectl traffic using mitmproxy.

This technique is inspired by/informed by Ahmet Alp Balkan’s similarly-named blog post from 2019. Unfortunately, I found the instructions there to be incomplete (most likely just due to the passage of time and continued evolution of the tools involved).

I used the following tools and environments in my testing:

  • The tests were conducted on a Linux system running Ubuntu 24.04.4. The commands should work similarly on macOS.
  • Mitmproxy was installed from the Ubuntu repositories using apt.
  • kubectl version 1.33.3 was used to communicate to a self-managed cluster Continue reading

What’s New in Calico: Winter 2026 Release

AI Powered Intelligence, Unified Traffic Observability and Scalable Infrastructure Management

As anyone managing one or more Kubernetes clusters knows by now, scaling can introduce an exponentially growing number of problems. The sheer volume of metrics, logs and other data can become an obstacle, rather than an asset, to effective troubleshooting and overall cluster management. Fragmented tools and manual troubleshooting processes introduce operational complexity leading to the inevitable security gaps and extended downtime. As the number of clusters grows it becomes more important than ever to find ways of reducing the observability noise, decluttering the monitoring stack and eliminating the bottlenecks that get in the way of keeping your clusters stable and secure.

The Winter 2026 release of Calico Enterprise and Calico Cloud addresses the pain points of scaling clusters with three key enhancements:

1. AI-Powered Intelligence

AI Assistant for Calico: Efficiently navigate disparate data sources to quickly get answers through natural language, or proactively identify problems before they arise.

2. Unified Traffic Observability

GSMA Open Gateway offers developers one API for 300+ mobile networks

Developers care about protocols, standards, and specifications — a little. But it’s not what keeps them up at night. Your average software engineer cares more about feature functionalities, performance, debugging, misconfigurations, and keeping infrastructure complexity under control. If a given component of a technology stack doesn’t align to those goals, it rarely makes it into the developer’s “backlog,” the strategic tracker that monitors application features, enhancements, and fixes. These home truths might have made leaders at the GSMA, an advocacy and lobbying organization for the mobile communications industry, anxious, because their

D2DO295: Risks and Benefits of Putting AI in Production

Engineers and developers are using AI like never before, including in production. That has potential consequences, both good and bad, for uptime, operations, security and risk management, and more. Today’s guest, Rich Mogull, guides us through the decision-making process of adding AI to your production lifecycle and possible ramifications. Rich is Chief Analyst at the... Read more »

Always-on detections: eliminating the WAF “log versus block” trade-off

Traditional Web Application Firewalls typically require extensive, manual tuning of their rules before they can safely block malicious traffic. When a new application is deployed, security teams usually begin in a logging-only mode, sifting through logs to gradually assess which rules are safe for blocking mode. This process is designed to minimize false positives without affecting legitimate traffic. It’s manual, slow and error-prone.

Teams are forced into a trade-off: visibility in log mode, or protection in block mode. When a rule blocks a request, evaluation stops, and you lose visibility into how other signatures would have assessed it — valuable insight that could have helped you tune and strengthen your defenses.

Today, we’re solving this by introducing the next evolution of our managed rules: Attack Signature Detection.

When enabled, this detection inspects every request for malicious payloads and attaches rich detection metadata before any action is taken. You get complete visibility into every signature match, without sacrificing protection or performance. Onboarding becomes simple: traffic is analyzed, data accumulates, and you see exactly which signatures fire and why. You can then build precise mitigation policies based on past traffic, reducing the risk of false positives.

But we’re going one step further. Continue reading

Mind the gap: new tools for continuous enforcement from boot to login

One of our favorite ask-me-anything questions for company meetings or panels at security conferences is the classic: “What keeps you up at night?”

For a CISO, that question is maybe a bit of a nightmare in itself. It does not have one single answer; it has dozens. It’s the constant tension between enabling a globally distributed workforce to do their best work, and ensuring that "best work" does not inadvertently open the door to a catastrophic breach.

We often talk about the "zero trust journey," but the reality is that the journey is almost certainly paved with friction. If security is too cumbersome, users find creative (and dangerous) ways around it. If it’s seamless at the cost of effectiveness, it might not be secure enough to stop a determined adversary.

Today, we are excited to announce two new tools in Cloudflare’s SASE toolbox designed to modernize remote access by eliminating the "dark corners" of your network security without adding friction to the user experience: mandatory authentication and Cloudflare’s own multi-factor authentication (MFA). 

Addressing the gap between installation and enforcement

When you deploy the Cloudflare One Client, you gain incredible visibility and control. You can apply Continue reading

The Tale of Two EVPN/MPLS Encapsulations

I decided it was high time to create EVPN/MPLS netlab integration tests and wanted to use the same approach I used for the EVPN/VXLAN ones:

  • One of the PE-devices is the device we want to test
  • The other PE-device is a device that is known to work (ideally, an FRRouting container).
  • Bonus points if the other PE-device can generate operational data in JSON format. Using a device for which we already have a validation plugin is close to perfection.
  • Add a P-router in the middle because MPLS.
  • Attach some hosts to the two PE-devices (we’re testing two MAC-VRFs in the final version of the test)
  • After validating everything that can reasonably be validated (OSPF session, IBGP session, EVPN AF on IBGP session), do the end-to-end pings and hope for the best.

This is the graph netlab created from the lab topology:

Read more …

Defeating the deepfake: stopping laptop farms and insider threats

Trust is the most expensive vulnerability in modern security architecture. In recent years, the security industry has pivoted toward a zero trust model for networks — assuming breach and verifying every request. Yet when it comes to the people behind those requests, we often default back to implicit trust. We trust that the person on the Zoom call is who they say they are. We trust that the documents uploaded to an HR portal are genuine.

That trust is now being weaponized at an unprecedented scale.

In our 2026 Cloudflare Threat Report, we highlight a rapidly accelerating threat vector: the rise of "remote IT worker" fraud. Often linked to nation-states, including North Korea, these are not just individual bad actors. They are organized operations running laptop farms: warehouses of devices remotely accessed by workers using stolen identities to infiltrate companies, steal intellectual property (IP), and funnel revenue illicitly.

These attackers have evolved and continue to do so with advancements in artificial intelligence (AI). They use generative AI to pass interviews and deepfake tools to fabricate flawless government IDs. Traditional background checks and standard identity providers (IdPs) are no longer enough. Bad actors are exploiting an identity assurance gap, Continue reading

Moving from license plates to badges: the Gateway Authorization Proxy

We often talk about the "ideal" state, one where every device has a managed client like the Cloudflare One Client installed, providing deep visibility and seamless protection. However, reality often gets in the way.

Sometimes you are dealing with a company acquisition, managing virtual desktops, or working in a highly regulated environment where you simply cannot install software on an endpoint. You still need to protect that traffic, even when you don’t fully manage the device.

Closing this gap requires moving the identity challenge from the device to the network itself. By combining the browser’s native proxy capabilities with our global network, we can verify users and enforce granular policies on any device that can reach the Internet. We’ve built the Gateway Authorization Proxy and Proxy Auto-Configuration (PAC) File Hosting to automate this authentication and simplify how unmanaged devices connect to Cloudflare.

The problem: sometimes IP addresses aren't enough

Back in 2022, we released proxy endpoints that allowed you to route traffic through Cloudflare to apply filtering rules. It solved the immediate need for access, but it had a significant "identity crisis."

Because that system relied on static IP addresses to identify users, it was a bit like a Continue reading

Stop reacting to breaches and start preventing them with User Risk Scoring

Most security teams spend their days playing a high-stakes game of Whac-A-Mole. A user’s credentials get phished, or they accidentally download a malicious file, and suddenly you’re in incident response mode. 

We built our SASE platform, Cloudflare One, to stop that cycle. By placing Access and Gateway in front of your applications and Internet traffic, we gave you the tools to decide who gets in and where they can go.

Today, we’re making those decisions smarter. You can now incorporate User Risk Scores directly into your zero trust network access (ZTNA) policies. Instead of just checking "Who is this user?" and "Is their device healthy?", you can now ask, "How has this user been behaving lately?" and adjust their access in real time.

Step 1: From "what" to "how"

For years, traditional corporate access was binary. You either had the right login and the right certificate, or you didn’t. But identity is fluid. A legitimate user can become a risk if their account is compromised or if they start exhibiting "insider threat" behaviors — like impossible travel, multiple failed login attempts, or triggering data loss prevention rules by moving sensitive data.

Cloudflare One now Continue reading

Containerlab Network Emulator v0.73 Review

I first reviewed Containerlab in 2021 when it was a promising but relatively new container-based network emulator. Five years later, Containerlab has matured into a polished, developer-friendly platform with a rich ecosystem of tools around it. In this post, I will revisit Containerlab and cover what has changed since my original review.

What is Containerlab?

Containerlab is an open-source, container-based network emulation platform that lets you build, run, and tear down realistic network topologies using simple, declarative YAML files. It uses lightweight containers and Linux networking to interconnect routers, switches, hosts, and tools into reproducible labs that behave like real networks. It also supports virtual machines, so it can run many commercial router images.

Containerlab integrates cleanly with automation tools such as Ansible, Nornir, and CI/CD pipelines, and emphasizes “lab-as-code” workflows. It is well suited for network automation development, validating designs and configuration changes, and learning about complex scenarios like BGP, EVPN, or data-center fabrics on a single workstation or server.

The project was originally developed by Nokia engineers and is hosted on GitHub. It has grown into one of the most widely-used open-source network lab platforms, with an active community on Discord and a dedicated documentation site.

What’s Changed Continue reading

Evolving Cloudflare’s Threat Intelligence Platform: actionable, scalable, and ETL-less

For years, the cybersecurity industry has suffered from a "data gravity" problem. Security teams are buried under billions of rows of telemetry, yet they remain starved for actionable insights. 

A Threat Intelligence Platform (TIP) is a centralized security system that collects, aggregates, and organizes data about known and emerging cyber threats. It serves as the vital connective tissue between raw telemetry and active defense.

The underlying architecture of Cloudflare’s Threat Intelligence Platform sets it apart from other solutions. We have evolved our Threat Intelligence Platform to eliminate the need for complex ETL (Extract, Transform, Load) pipelines by using a sharded, SQLite-backed architecture. By running GraphQL directly on the edge, security teams can now visualize and automate threat response in real time. Instead of one massive database, we distribute Threat Events across thousands of logical shards — meaning sub-second query latency, even when aggregating millions of events across global datasets.

By unifying our global telemetry with the manual investigations performed by our analysts, our intelligence platform creates a single source of truth that allows security teams to move from observing a threat to preemptively blocking it across the Cloudflare network. We believe your intelligence platform shouldn't just tell you that Continue reading

Introducing the 2026 Cloudflare Threat Report

Today’s threat landscape is more varied and chilling than ever: Sophisticated nation-state actors. Hyper-volumetric DDoS attacks. Deepfakes and fraudsters interviewing at your company. Even stealth attacks via trusted internal tools like Google Calendar, Dropbox, and GitHub.

After spending the last year translating trillions of network signals into actionable intelligence, Cloudforce One has identified a fundamental evolution in the threat landscape: the era of brute force entry is fading. In its place is a model of high-trust exploitation that prioritizes results at all costs. In order to equip defenders with a strategic roadmap for this new era, today we are releasing the inaugural 2026 Cloudflare Threat Report. This report provides the intelligence organizations need to navigate the rise of industrialized cyber threats.

The new barometer for risk: Measure of Effectiveness (MOE)

Cloudforce One has observed a broader shift in attacker psychology. To understand how these methods win, we have to look at the why behind them: the Measure of Effectiveness, or MOE.

In 2026, the modern adversary is trading the pursuit of "sophistication" (complex, expensive, one-off hacks) in favor of throughput. MOE is the metric attackers use to decide what to exploit next. It is a cold calculation of the Continue reading

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