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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  • The details registered about me/my company are incorrect or out of date.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

Rogue Whois servers are a big security risk

Cancelled domain names are liable to be abused

Skull shape in a blue digital environment
  • Wednesday 19 February 2025

Last month, ICANN issued a warning about cybercriminals operating 'rogue' Whois servers. The warning made uncomfortable reading for the industry, because the scam flagged up by ICANN relied on domain names previously used for legitimate Whois servers, then allowed to lapse. If snapped up by scammers, such domain names can be used to mimic legitimate Whois servers, in order to hack users or steal their identities.

What's a rogue Whois server?

A Whois server is a database in which domain registration data is stored and made available to the public. Internet users can then look up registration data about domain names, such as registrants' contact details. That kind of information is important to organisations that issue TLS certificates, transfer domain names or send notice-and-take-down requests, for example. Until recently, all registries for generic top-level domains were obliged to operate Whois servers.

Since last year, however, any registry that operates an RDAP service is no longer required to offer Whois as well. When the rules changed, many registries retired their Whois servers, often as a cost-saving measure. In some cases, the domain names previously used for the servers were cancelled as well. And it now seems that the dropped domain names can be re-registered and used for rogue Whois servers, i.e. malicious servers for legitimate domains. A rogue server enables a crook to do things such as obtain fraudulent SSL certificates for phishing sites.

Danger flagged up by recent research

Security expert Benjamin Harris demonstrated the danger last year by registering the lapsed domain name dotmobiregistry.net, previously used for the authoritative Whois server for .mobi domains. After setting up his own Whois server and populating it with false information, he managed to issue false HTTPS certificates, intercept communications and imitate legitimate websites. It was Harris's investigation that prompted ICANN to issue its warning.

The uncomfortable aspect of the disclosures is that Harris exploited a vulnerability that would never have existed if the defunct server's domain name had simply been retained. The risks associated with cancelling sensitive domain names should be known to a registry better than to anyone. We have often highlighted the risks ourselves. It's also striking how many registrars and certificate authorities (CAs) automatically went on trying to query the Whois server after it had been taken down. They too should have noticed that something was amiss much sooner.

Importance of RDAP emphasised

The issue of rogue Whois servers shows again that there's still a lot of room for improvement where domain name data and the associated processes are concerned. Whois is an aging protocol, which cannot offer the kind of structured access to domain name information provided by the RDAP protocol. With RDAP, the results of a domain name look-up are reported in JSON format, making them is easy to process. Although RDAP can't prevent human errors, such as cancelling the domain previously used for a trusted service, it does support authentication and access control. Here at SIDN, we began by introducing RDAP for the .amsterdam and .politie extensions. And, since April 2024, we've offered an RDAP service for .nl as well. Users can look up details of a domain name by generating an RDAP URL with '/domain' or '/domeinnaam' followed by the domain name in question, e.g. https://rdap.sidn.nl/domain/sidn.nl.

Because the Whois era is approaching its end, we would advise everyone to migrate to RDAP. We're continuing to operate our Whois services for now, but they'll ultimately be decommissioned.

Advice

Finally, a word of important advice: never let an important domain name's registration lapse, even if the name's no longer used for any active services. The security risk is simply too great!