Greywell Cyber

Boutique cyber security, UK

Boutique Cyber Security, Delivered by the People You Meet.

We build websites, mobile apps and software that take the tedious work off your team, and we design, test and defend the networks underneath them. We take on a select number of engagements, so the senior people who scope your work are the people who deliver it.

Why Boutique

Greywell Cyber was founded by critical infrastructure, digital forensics and incident response practitioners. We are selective about the engagements we take, which keeps senior people on every piece of work from the first call to the final report and gives you a direct line to the person doing it.

Every engagement is scoped and contracted before work starts: what is in scope, what it costs, who does the work and when you will have the results. Reports are written for the engineers who will act on them and the board that has to decide.

Dealing with an incident? Email security@greywellcyber.com with URGENT in the subject line. Retained clients use the route in their contract. More on digital forensics and incident response.

Free Network Tools

Built and maintained by us, free for anyone to use. The calculators and generators run in your browser and need no account; the quiz takes a free one, so your progress is saved.

  • Subnet Calculator

    IPv4 and IPv6. Network, broadcast, host range, mask and wildcard at a glance.

  • VLSM Planner

    Split one IPv4 block into named subnets of different sizes, largest first, with the spare space shown.

  • Networking and Subnetting Quiz

    Practice questions across twelve topics, from subnetting maths to OT risk. Free with an account, so your progress is saved.

Also: the route summariser, the security headers checker and our guides to IPv4 Network Design and IPv6 Design .