- ExpressVPN Develops CSAM Blocking Tool in Partnership with IWF
- OpenBoundary blocks known CSAM domains at the DNS level
- The tool is open source so that other services can integrate it.
As regulators around the world scramble to find solutions to increase children’s safety online, VPN services are frequently targeted for their alleged role in facilitating anonymous access to illegal content.
ExpressVPN is now taking a proactive stance against one of the most heinous crimes on the internet by creating a dedicated tool that stops access to child sexual abuse material (CSAM).
The provider partnered with the Internet Watch Foundation (IWF) to develop Open limita set of server-level tools designed to help network operators restrict access to verified CSAM domains securely and transparently.
ExpressVPN maintains that OpenBoundary is built on a privacy-first infrastructure, introducing safeguards throughout the network without disrupting or violating its strict no-logs policy.
Dr. Peter Membrey, director of research at ExpressVPN, told TechRadar that the move is a “safe first step to start the conversation” between technologists, child safety groups and regulators.
He added: “We believe there is no good reason for this material to exist or cross our networks, but it doesn’t have to be all or nothing.” He believes OpenBoundary provides regulators with “sharper tools” that don’t weaken encryption or user privacy in the name of security.
As part of the “Not on My Network” initiative, ExpressVPN is open sourcing OpenBoundary. The goal is for other VPN services, Internet Service Providers (ISPs), and cloud platforms to adopt the framework.
Kape Technologies’ fellow brands CyberGhost and Private Internet Access (PIA) are the first to join the mission. Kerry Smith, chief executive of the IWF, applauded the innovative approach and said the move “balances its commitment to children’s online safety and online privacy.”
How OpenBoundary works
The technical implementation of OpenBoundary is simple. The tool operates at the DNS level, blocking domains that appear on the human-verified IWF list.
This happens automatically when a user connects to the VPN application, preventing known CSAM domains from being loaded. Membrey explains that if a user tries to visit a flagged site, the system simply returns an error stating that the site does not exist.
Crucially, this process does not involve traffic inspection, monitoring, or encryption breaking. Instead, it’s a simple domain lock.
While some proponents argue that any content filtering contradicts the “neutral” nature of a VPN, Membrey says it is “comfortable blocking” sites that exclusively host CSAM material.
“We don’t want these things going through our network. We don’t want to be a part of this,” he told Techradar.
Closing the gap between security and privacy
Until now, the battle against CSAM content has largely focused on detecting illegal materials.
In the EU, the proposed law called Chat Control, which is now in its final legislative stage, has attracted strong resistance from politicians, scientists and technologists alike. Now, the UK is also accelerating CSAM scanning obligations under the Online Safety Act.
In both cases, critics have pointed out how current detection technologies (whether client-side scanning or hash matching) are technically ineffective, while inevitably damaging the privacy and security of all online services that are supposed to implement these checks.
ExpressVPN’s new tool is certainly not a technical solution to CSAM scanning and detection, but rather a way to recalibrate the discussion towards what we can do now. A first step to mitigate the problem and close the gap between privacy, security and protection of children on the Internet.
Commenting on this point, Membrey told TechRadar: “Our pitch is simple: ‘Not on my network’. We urge legislators to collaborate and innovate before legislating and regulating. It is much easier to undo a failed technological solution than to undo a general law passed by a parliament or congress.”
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