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Frequently asked questions

  • I am looking for a domain name registrant. Where can I look it up?

    The Whois is an easy-to-use tool for checking the availability of a .nl domain name. If the domain name is already taken, you can see who has registered it.

    On the page looking up a domain name you will find more information about what a domain name is, how the Whois works and how the privacy of personal data is protected. Alternatively, you can go straight to look for a domain name via the Whois.

  • I would like to transfer my domain name to another registrar. What is the procedure?

    To get your domain name transferred, you need the token (unique ID number) for your domain name. Your existing registrar has the token and is obliged to give it to you within five days, if you ask for it. The procedure for changing your registrar is described on the page transferring your domain name.

  • The details registered about me/my company are incorrect or out of date. How can I get them updated?

    To update the contact details associated with your domain name, you need to contact your registrar. Read more about updating contact details.

  • Why is my domain name in quarantine?

    When a domain name is cancelled, we aren't told the reason, so we can't tell you. You'll need to ask your registrar. The advantage of quarantine is that, if a name's cancelled by mistake, you can always get it back.

    One common reason is that the contract between you and your registrar says you've got to renew the registration every year. If you haven't set up automatic renewal and you don't renew manually, the registration will expire.

  • Ik heb een klacht over mijn provider/registrar. Kan ik daarvoor bij SIDN terecht?

    Wanneer je een klacht hebt over of een geschil met je registrar dan zijn er verschillende mogelijkheden om tot een oplossing te komen. Hierover lees je meer op pagina klacht over registrar. SIDN heeft geen formele klachtenprocedure voor het behandelen van een klacht over jouw registrar.

  • What conditions do I have to meet as a registrar?

    Would you like to be able to register domain names for customers or for your own organisation by dealing directly with SIDN? If so, you can become a .nl registrar. Read more about the conditions and how to apply for registrar status on the page becoming a registrar.

More frequently asked questions

Tech report: 3 years of using LEMMINGS to prevent data breaches

Tool helps prevent leaks of confidential e-mails

Concept of email messages in a virtual space

The original blog is in Dutch. This is the English translation of it.

Since June 2021, our LEMMINGS tool has been monitoring cancelled .nl domain names in order to help prevent confidential e-mails getting into the wrong hands. We've now put together an extensive tech report describing the design, implementation and evaluation of LEMMINGS. We hope it'll inspire other registries and registrars to address this data security issue.

Why cancelled domain names are a risk

Registrants sometimes cancel their .nl domain names when they don't need them anymore. That happens if, for example, the domain name was registered for a business that's stopped trading, a campaign that's ended, or a product that's been discontinued. After a period in quarantine, a cancelled domain name can be re-registered and used by anyone. That can lead to the new registrant getting e-mail meant for the old registrant. Which in turn can cause a data breach, as happened to the Dutch police and certain health care providers.

So, in 2021, we developed LEMMINGS, a tool whose name is an acronym of deLetEd doMain Mail warNinG System. LEMMINGS alerts the ex-registrants of recently cancelled .nl domain names if we see signs that their old domains are still attracting e-mail traffic. Signs of continued mail activity are picked up purely by analysing the DNS traffic we process for .nl.

For additional information about LEMMINGS, check out our previous publications: our blogs about the initial pilot and the upscaling of the pilot, as well as the presentations we prepared for wider audiences (e.g. at CENTR or the ONE conference).

Extensive tech report

We have now published a tech report, in which we discuss our design choices, the technical details and the impact of LEMMINGS in more detail. The report's conclusion is that LEMMINGS has raised the profile of the problem and may also have prevented some data breaches, but the latter is difficult to demonstrate with certainty.

We hope that our detailed new report will provide greater insight into how LEMMINGS works, and will inspire other registries and registrars to address the danger of data breaches linked to cancelled domain names.

LEMMINGS stays on

In the future, DNS data minimisation technologies such as QNAME minimisation may have significant impact on LEMMINGS' effectiveness. After talking to the Registrars' Association, we've decided to keep LEMMINGS running for now, and to continue warning ex-registrants about potential data breaches. In the meantime, we'll start assessing the potential impact of new technologies on LEMMINGS' effectiveness.

Got a question? See a research opportunity?

Do you have a question, or an idea for using LEMMINGS in the context of research that could contribute to the security of .nl and the wider internet? Drop a line to Moritz Müller at moritz.muller@sidn.nl.

Article by:

Moritz Muller

Moritz Müller

Research engineer