Domain Name Service

DNS servers are not only used for classic surfing on the Internet. Because actually all services use the DNS system to determine the IP addresses to an FQDN. Most users do not pay much attention to the Domain Name System (DNS) and do not think about investing in the security of the DNS layer. After all, the hallmark of a well-functioning DNS service is its invisibility and ability to correctly connect users to websites or web applications without delay.

The DNS protocol does not contain any authentication to ensure that one is really connected to the desired DNS server. DNS requests can be redirected by the provider to its own censoring servers. For the user, securing the DNS layer means that malicious domains, IP addresses and cloud applications are blocked before a connection is even made. On the other hand, for the administrator of the DNS server, it means that it has mechanisms that ideally prevent misuse/redirection, but at least deliver validated DNS responses.

Latest posts Blog Page

Blog entries

DNS tunnel

DNS tunnel

The idea behind using a tunnel based on DNS is to hide all outgoing traffic from others. This means translating human-readable host names into numeric IP addresses through DNS and vice versa.

DNS DDoS Precaution

Precaution against DNS Amplification Attacks

The DNS amplification attack is one of the DDoS attacks. This is because the attacker exploits misconfigured name servers and forwards huge data streams to the victim's internet connection with the misconfigured name servers. As a result of the redirection, the victim's internet connection is overloaded and can no longer be used. This is all the more fatal in times of cloud-based data centres. This article names RFCs to take precautions against such an attack.


CADR - DNSSEC Authenticated DNS Registry

CADR (a somewhat contrieved acronym for "DNSSEC Authenticated DNS Registry") is a registry for DNS data. I.e. CADR is a system in the same ballpark as registries run by TLDs to manage delegation information or, in some environments, run by registrars to manage delegation information for customers for further propagation to a registry (typically for a TLD).

A few basic things to DNS


What are DNS security extensions and which resource records are added?

The DNS security extensions specified in [RFC4033], [RFC4034] and [RFC4035], in contrast to the TSIG mechanism, which focuses on securing the transaction channel, aim at securing data objects of a zone. 

The authenticity and integrity of said zone data objects, the so-called Resource Record Sets (RRset ), is ensured by creating a digital signature via the respective RRset. Asymmetric, zone-specific key pairs are used to generate the RRset signatures.

DNSSEC RR  (RRSIG)Contains the signature via an RRset; in addition to signatures via the usual DNS RRsets, signatures are also formed via DNSSEC RRsets (DNSKEY, DS, NSEC) and stored in corresponding RRSIG records. RRSIG RRs carry a time stamp ("Signature Expiration Date"), which determines the validity period of the signature.
DNSKEYContains a published base64-encoded public key that can be used to verify the signature in an RRSIG RR as part of the authentication process. Found at the zone delegation point of a parent zone and contains a reference to the DNSKEY RR (public key) of a child zone, with whose corresponding private key either the DNSKEY RRset in the zone apex of the child zone or the other RRsets of the child zone were signed. DS RRs are essential for setting up so-called "authentication chains" to verify signed data objects across domain boundaries.
NSECContains two types of information:
  • The next canonical (owner) name containing authoritative data or an NS RRset at a delegation point. The RRset types associated with
  • The current canonical (owner) name Chains of (signed) NSEC RRs allow authentication of negative responses (non-existence of canonical (owner) names or RR types).


What does transactional signatures (TSIG) stand for and what does it involve?

All communication within the DNS protocol is based on so-called DNS messages. 

Especially the DNS messages exchanged between two name servers in the context of zone transfers, namely DNS NOTIFY message(s) from the master (or also slave) to the slave and DNS AXFR/IXFR request/response messages between slave and master (or between slaves), can be protected by using a symmetric cryptography procedure on the transaction level. 

This mechanism, called Transaction Signatures, is specified in [RFC2845] and uses a "shared secret" - i.e. a common symmetric key - to sign the DNS messages exchanged between two parties. 

Corresponding "Access Control Lists" (ACL) (based on this shared secret) are also used to control whether the DNS messages mentioned are accepted by the other party at all. 

If one of the name servers involved has generated a corresponding outgoing message, a "Keyed One-Way Hash Function" is applied to this message to generate a 128-bit "Message Digest" before it is actually sent. The symmetric key shared by the sending and receiving parties is used as the key.


What does split namespace mean?

In more complex DNS topologies, separation between generally and restrictedly visible zone information is usually required. This type of NS configuration, called "split namespace", is usually used on specially secured systems of a "de-militarised zone" (DMZ), the so-called "bastion hosts". The split namespace configuration of a DMZ name server instance usually has the following properties: 

  • Provision of a deliberately small set of official and publicly available resource records (so-called "external view" or also "shadow namespace") of a domain for resolving queries from external DNS clients. Typical examples are the SOA record of the domain, NS records, MX records for the email exchange, as well as a few A records and their respective PTR records. 
  • Ability to resolve internal names and IP addresses in parallel with external resolving, although the use of this capability is usually limited to queries from the DMZ (and possibly from the intranet).


What does split function name server mean?

In principle, name servers answer two types of queries: iterative and recursive. 

For security reasons, this behaviour must be limited to the absolutely necessary extent without calling into question the usability of the service itself. Hierarchically structured namespaces and the physical segmentation of network topologies make it possible to define classes of name servers in which the aforementioned types of queries are either completely separated from each other or can be restricted locally with regard to their availability.


What does Nonrecursive Name Server stand for?

A name server that basically does not answer recursive queries and does not build up a corresponding data cache. Examples of this are the NS of the (Internet) root domain and (usually) hidden primary master name servers.


What is a forwarder?

A name server that is the recipient of recursive queries forwarded to it by remote name servers. Said remote NS use a forwarding configuration by means of which selected or all recursive queries received by them are passed on as such to one or more forwarders.


What is a caching-only name server?

A name server that is not authoritatively responsible for any zone. The only function of this NS type is to determine requested RRs from other name servers and to hold them in its cache (to answer corresponding requests).


What is a hidden slave name server?

A slave name server that is not listed in the NS records of the zones for which it is authoritative. This ensures that this (additional) name server does not negatively affect the size limitation of UDP-based DNS response messages and that remote name servers cannot follow any delegation to this slave.


What is a stealth slave name server?

A slave name server, which instead of the hidden primary master name server appears externally in the role of the primary master name server. In order to fulfil this role, this server is not only listed - as usual - in the NS records of the zone for which it is authoritative, but also entered in the SOA records (MNAME field) of the said zone.


What is a hidden primary master name server?

A hidden primary master name server is not listed in the name server records of the zone (in the zone file) for which it is actually authoritatively responsible. This ensures that remote name servers cannot follow any delegation to this real master name server. Thus, the master name server is "hidden". This type of DNS design is mostly used in security architectures or in small companies.


What is a secondary name server?

The synonym for a secondary name server is slave name server. A secondary name server is a redundant authoritative name server for a particular zone. The name server instance receives its zone data from the primary master name server or another slave name server.


What is a primary master name server?

A primary master name server is an authoritative name server for a specific zone (e.g.; the actual zone data is maintained within the name server instance.


What is an iterative request?

This query type is used in the communication between name servers when they process a recursive query (quasi in cooperation). 

If, for example, a recursive query is made for the IP address of, the requested name server first checks whether the authoritative name servers for the domain are known to it. If this is the case, the name server sends a corresponding iterative query to one of these servers; otherwise, one of the authoritative de name servers (if known) and, in the last instance, one of the (Internet) root name servers is queried. The name server that receives an iterative query delivers the best possible answer found in its local database (including cache) as a result. This is either the actually requested IP address (or the requested name) or a referral list containing all authoritative name servers "closer" to the target of the request. If the requesting name server administers so-called Round Trip Times (RTT) for the servers named in the referral list on the basis of previous requests, it selects the one with the lowest RTT and repeats the iterative request there. This process continues until an actual answer is received.


What is a recrusive request?

This type of query is initiated by (stub) resolver hosts or by name servers using forwarders. 

Recursive name resolution queries assign the exclusive task of performing all necessary steps to fulfil the request to the requested NS system. Delegation of the steps to other name servers or the return of referrals to the requesting client are not provided for or permitted. 

The addressed name server can either answer the request directly or iteratively request other name servers until an answer is available.

In accordance with the legal requirements of data protection law (in particular the BDSG as amended and the European Data Protection Regulation 'DS-GVO'), we inform you below about the nature, scope and purpose of the processing of personal data by our company. This privacy policy also applies to our websites and social media profiles. With regard to the definition of terms such as "personal data" or "processing", we refer to Art. 4 DS-GVO.

Name and contact details of the person(s) responsible

Our responsible person(s) (hereinafter "responsible person") within the meaning of Art. 4 fig. 7 DS-GVO is:
Jens Mahnke
Karl-Kunger-Str. 56
12435 Berlin Germany
Email address:

Types of data, purposes of processing and categories of data subjects

Below we inform you about the type, scope and purpose of the collection, processing and use of personal data. 

1. types of data we process
Usage data (access times, websites visited, etc.), communication data (IP address, etc.),

2. purposes of the processing according to Art. 13 para. 1 c) DS-GVO
Technical and economic optimisation of the website, optimisation and statistical evaluation of our services, improving user experience, compilation of statistics,

3. categories of data subjects according to Art. 13 (1) (e) DS-GVO
Visitors/users of the website,

The data subjects are collectively referred to as "users".

Legal basis for the processing of personal data

Below we inform you about the legal basis for the processing of personal data. 1. if we have obtained your consent for the processing of personal data, Art. 6 para. 1 sentence 1 lit. a) DS-GVO is the legal basis. 2. if processing is necessary to comply with a contract or to carry out pre-contractual measures in response to your request, Art. 6 (1) sentence 1 lit. b) DS-GVO is the legal basis. If the processing is necessary to comply with a legal obligation to which we are subject (e.g. statutory retention obligations), Art. 6 (1) sentence 1 lit. c) DS-GVO is the legal basis. If the processing is necessary to protect the vital interests of the data subject or another natural person, the legal basis is Art. 6 (1) sentence 1 lit. d) DS-GVO. If the processing is necessary to protect our legitimate interests or the legitimate interests of a third party and your interests or fundamental rights and freedoms are not overridden in this respect, Art. 6 para. 1 sentence 1 lit. f) DS-GVO is the legal basis.

Disclosure of personal data to third parties and order processors

As a matter of principle, we do not pass on any data to third parties without your consent. However, if this should be the case, then the data will be passed on on the basis of the aforementioned legal grounds, e.g. when data is passed on to online payment providers for the fulfilment of a contract or due to a court order or because of a legal obligation to hand over the data for the purpose of criminal prosecution, to avert danger or to enforce intellectual property rights. We also use processors (external service providers e.g. for web hosting of our websites and databases) to process your data. If data is passed on to the processors as part of a contract processing agreement, this is always done in accordance with Art. 28 DS-GVO. In doing so, we select our processors carefully, monitor them regularly and have been granted a right to issue instructions regarding the data. In addition, the processors have to have taken suitable technical and organisational measures and comply with the data protection regulations according to the BDSG n.F. and the DS-GVO.

Data transfer to third countries

The adoption of the European General Data Protection Regulation (GDPR) has created a uniform basis for data protection in Europe. Your data is therefore predominantly processed by companies to which the GDPR applies. However, if processing is carried out by services of third parties outside the European Union or the European Economic Area, these have to fulfil the special requirements of Art. 44 ff. DS-GVO must be complied with. This means that the processing takes place on the basis of special guarantees, such as the officially recognised determination by the EU Commission of a level of data protection corresponding to the EU or the observance of officially recognised special contractual obligations, the so-called "standard contractual clauses". Insofar as we obtain your express consent to the transfer of data to the USA due to the invalidity of the so-called "Privacy Shield" in accordance with Article 49 (1) sentence 1 lit. a) DSGVO, we point out in this regard the risk of secret access by US authorities and the use of the data for monitoring purposes, possibly without any legal remedy for EU citizens.

Deletion of data and storage period

Unless expressly stated in this data protection declaration, your personal data will be erased or blocked as soon as you revoke the consent given for processing or the purpose for storing the data no longer applies or the data are no longer required for the purpose, unless their continued storage is necessary for evidence purposes or is contrary to statutory retention obligations. This includes, for example, retention obligations under commercial law for business letters in accordance with § 257 para. 1 of the German Commercial Code (HGB) (6 years) and retention obligations under tax law for receipts in accordance with § 147 para. 1 of the German Fiscal Code (AO) (10 years). When the prescribed retention period expires, your data will be blocked or deleted unless the storage is still necessary for the conclusion or fulfilment of a contract.

Existence of automated decision making

We do not use automated decision making or profiling.

Provision of our website and creation of log files

1. If you use our website for information purposes only (i.e. no registration and no other transmission of information), we only collect the personal data that your browser transmits to our server. If you wish to view our website, we collect the following data:

  • IP address;
  • Internet service provider of the user; 
  • Date and current time of the request;
  • browser type;
  • language and browser version;
  • Content of the retrieval;
  • Time zone;
  • Access status/HTTP status code;
  • Amount of data;
  • Websites from which the request came;
  • Operating system.

This data is not stored together with other personal data about you.

2. This data serves the purpose of user-friendly, functional and secure delivery of our website to you with functions and content as well as its optimisation and statistical evaluation.

3. The legal basis for this is our legitimate interest in data processing in accordance with Art. 6 (1) sentence 1 lit. f) DS-GVO, which also lies in the above purposes.

4. For security reasons, we store this data in server log files for a storage period of 70 days. After this period, they are automatically erased, unless we need to keep them for evidence purposes in the event of attacks on the server infrastructure or other legal violations.

Contacting us via contact form / email / fax / post

1. When contacting us via contact form, fax, mail or email form, your data will be processed for the purpose of handling the contact request.

2. If you have given your consent, the legal basis for processing your data is Art. 6 (1) sentence 1 lit. a) DS-GVO. The legal basis for the processing of data transmitted in the course of a contact request or email form, letter or fax is Art. 6 para. 1 p. 1 lit. f) DS-GVO. The responsible party has a legitimate interest in processing and storing the data in order to be able to answer users' enquiries, to preserve evidence for liability reasons and, if necessary, to be able to comply with its statutory retention obligations for business letters. If the objective of the contact is the conclusion of a contract, the additional legal basis for the processing is Article 6 (1) sentence 1 lit. b) DS-GVO.

3. We may store your details and contact request in our Customer Relationship Management System ("CRM System") or similar system.

4. The data is erased as soon as it is no longer required to achieve the purpose for which it was collected. For the personal data from the input mask of the contact form and those sent by email form, this is the case when the respective conversation with you has ended. The conversation is ended when it is clear from the circumstances that the matter in question has been conclusively clarified. We store enquiries from users who have an account or contract with us until two years after termination of the contract. In the case of legal archiving obligations, deletion takes place after their expiry: end of commercial law (6 years) and tax law (10 years) retention obligation.

5. You have the option to revoke your consent to the processing of personal data at any time in accordance with Art. 6 para. 1 p. 1 lit. a) DS-GVO. If you contact us by email form, you can object to the storage of personal data at any time.

Rights of the person concerned

1. Objection or revocation against the processing of your data

Insofar as the processing is based on your consent pursuant to Art. 6 para. 1 sentence 1 lit. a), Art. 7 DS-GVO, you have the right to revoke your consent at any time. This does not affect the lawfulness of the processing carried out on the basis of the consent until the revocation.

Insofar as we base the processing of your personal data on the balance of interests pursuant to Art. 6 (1) p. 1 lit. f) DS-GVO, you may object to the processing. This is the case if the processing is not necessary, in particular, for the compliance with a contract with you, which is shown by us in each case in the following description of the functions. When exercising such an objection, we ask you to explain the reasons why we should not process your personal data as we have done. In the event of your justified objection, we will review the merits of the case and either cease or adapt the data processing or show you our compelling legitimate grounds on the basis of which we will continue the processing.

You can object to the processing of your personal data for the purposes of advertising and data analysis at any time. You can exercise the right to object free of charge. You can inform us of your advertising objection using the following contact details: Jens Mahnke
Karl-Kunger-Str. 56 12435 Berlin Germany
Email address:

2. Right to information You have a right to information about your personal data stored by us in accordance with Art. 15 DS-GVO. This includes, in particular, information about the processing purposes, the category of personal data, the categories of recipients to whom your data has been or will be disclosed, the planned storage period, the origin of your data if it has not been collected directly from you.

3. Right to rectification You have the right to have inaccurate data corrected or correct data completed in accordance with Art. 16 DS-GVO.

4. Right to deletion You have the right to have your data stored by us deleted in accordance with Art. 17 DS-GVO, unless legal or contractual retention periods or other legal obligations or rights to further storage prevent this.

5. Right to restriction

You have the right to request a restriction in the processing of your personal data if one of the conditions in Art. 18 (1) a) to d) DS-GVO is complied with:

  • If you contest the accuracy of the personal data concerning you for a period of time which enables the controller to verify the accuracy of the personal data;
  • the processing is unlawful and you object to the erasure of the personal data and request instead the restriction of the use of the personal data;
  • the controller no longer needs the personal data for the purposes of the processing but you need them for the establishment, exercise or defence of legal claims; or
  • if you have lodged an objection to the processing pursuant to Art. 21 (1) DS-GVO and it is not yet clear whether the legitimate reasons of the controller outweigh your reasons.

6. Right to data portability You have a right to data portability in accordance with Art. 20 DS-GVO, which means that you can receive the personal data we hold about you in a structured, common and machine-readable format or request that it be transferred to another controller.

7. Right to complain You have the right to complain to a supervisory authority. As a rule, you can contact the supervisory authority for this purpose, in particular in the Member State of your place of residence, your workplace or the place of the alleged infringement.

Data security

In order to protect all personal data transmitted to us and to ensure that data protection regulations are complied with by us as well as by our external service providers, we have taken appropriate technical and organisational security measures. Therefore, among other things, all data is transmitted between your browser and our server via a secure SSL connection.

Status: 09/09/2022

Jens Mahnke 

Karl-Kunger-Strasse 56 

12435 Berlin 

Phone: 01717873970 

Email form: 

Disclaimer - legal information

§ 1 Warning about content 

The free and freely accessible contents of this website have been created with the greatest possible care. However, the provider of this website accepts no responsibility for the correctness and up-to-dateness of the free and freely accessible journalistic advice and news provided. Contributions identified by name reflect the opinion of the respective author and not always the opinion of the provider. The mere fact of calling up the free and freely accessible content does not create any contractual relationship between the user and the provider; in this respect, the provider's intention to be legally bound is lacking. 

§ 2 External links 

This website contains links to third-party websites ("external links"). These websites are subject to the liability of the respective operators. When the external links were first created, the provider checked the external content for any legal violations. At that time, no legal violations were apparent. The provider has no influence on the current and future design and content of the linked pages. The inclusion of external links does not imply that the provider adopts the content behind the reference or link as its own. It is not reasonable for the provider to constantly monitor the external links without concrete indications of legal violations. However, such external links will be erased immediately if legal violations become known. 

§ 3 Copyrights and ancillary copyrights

The contents published on this website are subject to German copyright and ancillary copyright law. Any use not permitted by German copyright and ancillary copyright law requires the prior written consent of the provider or the respective rights holder. This applies in particular to the copying, editing, translation, storage, processing or reproduction of content in databases or other electronic media and systems. Third-party content and rights are marked as such. The unauthorised reproduction or transmission of individual contents or complete pages is not permitted and is punishable by law. Only the production of copies and downloads for personal, private and non-commercial use is permitted. The display of this website in external frames is only permitted with written permission. 

§ 4 Special terms of use

Insofar as special conditions for individual uses of this website deviate from the aforementioned paragraphs, this will be expressly indicated at the appropriate place. In this case, the special terms of use shall apply in the respective individual case.