John Nielsen writes about practical cybersecurity and digital resilience for businesses. Nielsen's LinkedIn posts explain risks such as email spoofing, weak physical network access controls, and dependence on payment or software providers, then offer concrete steps companies can take.
26.2K followersBased on 15 posts · latest Oct 2026
Practical Danish-language cybersecurity and digital resilience posts for business audiences.
Best for
Editorially led Danish-language B2B campaign on cybersecurity and resilience.
Not for
Consumer lifestyle campaigns, short-form video, discount codes or mass consumer app downloads.
Key takeaways
A visitor can reach an internal network through an unguarded meeting-room port.
A forged email can misuse a company's domain; SPF, DKIM and DMARC have limits.
A payment-provider outage can stop sales; map provider chain and plan 48 hours.
Check first: Confirm audience fit and commercial terms, since no media kit or rates are published.
Main ideas
A familiar sender name is only as safe as the domain owner's instruction · Security testing should cover the front door, not only the network · Payment outages are a continuity decision, not just a technical failure
John Nielsen writes about practical cybersecurity and digital resilience for businesses.
Their LinkedIn posts show how risks can hide in ordinary processes: a visitor can reach an internal network, a forged email can misuse a company’s domain, or a payment-provider outage can stop sales.
They turn these scenarios into specific questions and checks for business leaders, IT teams and suppliers.
Nielsen connects concrete situations to technical and operational details, then gives readers a next step.
In their email-security posts, they use domain measurements to compare sectors and providers, and explain what SPF, DKIM and DMARC can—and cannot—protect against (Nielsen's analysis of email spoofing across providers).
They apply the same practical lens beyond email: a post about an unguarded meeting-room network port distinguishes a technical penetration test from a broader exercise that tests people, buildings and response (how an attacker might enter through the front door); a payment-outage post asks businesses to map their provider chain and plan for 48 hours without card payments (what to do when card payments stop).
John Nielsen's posts use cases to explain where routine business systems fail: a domain with no instruction, a meeting-room network port, a payment chain, a supplier exposed to foreign law or an automated deletion rule.
Read more
The recurring priority is clear ownership and a testable answer before an incident forces the question.
A familiar sender name is only as safe as the domain owner's instruction
Nielsen argues that email spoofing is often treated as an inbox-filter problem, but the decisive control sits with the organisation that owns the domain.
Read more
SPF and DKIM show whether a message came from an approved system; DMARC tells the recipient what to do when that check fails.
Without a quarantine or reject instruction, the recipient's filter alone decides.
They measure this by sector and urge organisations to inventory every system that sends mail, then set a dated plan.
They also warn that DMARC is no guarantee: a hosting provider that switches existing domains to reject without checking customers' senders could block legitimate mail.
A false boil-water notice went out in a water utility's name.
Of 798 water-utility domains checked, 663 did not ask recipients to reject mail sent in their name.
The count is domains, not utilities.
The examples range from water utilities and municipal domains to agencies, audit and accounting firms, property administrators and hosting providers. The underlying test stays the same.
Security testing should cover the front door, not only the network
Nielsen distinguishes three services buyers often blur.
Read more
A penetration test attacks selected technical systems.
Red teaming imitates a real attacker across technology, people and buildings.
Cyber security mystery shopping tests how far a visitor gets as a customer, supplier or guest.
They argue that a firewall or technical test cannot stop an attacker who has already walked into the meeting room.
Practical checks include counting active network ports, asking what happens when an unknown device connects and requiring tests that cover doors, people and response time.
They describe arriving at a customer's main entrance, greeting reception, sitting in an empty meeting room and plugging a network cable into the wall. Management agrees to the test in advance, and the visit is documented; a criminal does neither.
Payment outages are a continuity decision, not just a technical failure
Nielsen argues that a payment outage should be judged by what happens at the till, not only by its cause.
Read more
A technical fault and a ransomware attack can both stop card payments.
Payments depend on a terminal supplier, gateway, acquirer, processor and subcontractors; if one critical link fails, money stops even when the company's own systems are working.
They urge businesses to confirm offline payment capability, map the chain and decide in advance how to operate for 48 hours without cards.
Some shops had offline capability during the July outage but did not use it.
Two Nets card-payment outages, in July 2025 and May 2026, frame the argument.
Nielsen compares them with the February 2026 ransomware incident at BridgePay, when some US shops moved to cash and municipalities closed portals.
For the shop, the cause matters less than the same question at the checkout.
Foreign sanctions make supplier dependence a sovereignty question
Nielsen argues that sanctions and foreign law travel through commercial relationships, including banks, insurers and software suppliers.
Read more
A company may not be the direct target yet still lose access to a service when a supplier decides the legal risk is too high.
The management task is to list critical providers, note which country's law governs each and ask how they handle sanctions.
Test alternatives against the same exposure.
The ICC case shows the value of a plan B: the court had already moved office software and arranged replacements before sanctions hit the organisation.
After US sanctions against the International Criminal Court, AXA ended the court's health insurance on 1 October 2026; the ICC had another insurer ready. Nielsen also cites Amsterdam Trade Bank's 2022 collapse after sanctions led key suppliers to withdraw.
Automated deletion rules need testing like any other control
Nielsen treats automated deletion as a control that can fail quietly in either direction: removing records too early or keeping them too long.
Read more
Rules must use the right deadline, count from the right date and handle exceptions.
They recommend listing automated deletion rules with their legal basis and last check, testing the most important rule with data that should be kept, deleted or exempted, and clarifying how deletions are logged and corrected.
A deletion log is not a copy of the deleted data.
A citizen's inquiry exposed a missing decision in Denmark's Criminal Register.
Automatic routines had deleted some decisions too early for certain crime codes; the police estimated that about 60 of 1,400 crime codes were affected.
Nielsen applies the lesson to ordinary systems such as mail, ERP, document archives and CRM.
How does John explain the gap between a technical security test and the way an attacker might enter a workplace?
Read more
This post offers a practical, scenario-led approach.
John contrasts the familiar image of a hooded hacker with a neatly dressed visitor who walks into a meeting room and plugs into an unprotected network port.
They explain that this was an authorized test, then distinguish penetration testing from red teaming and “cyber security mystery shopping.”
They close with three checks: review active network ports, ask how unknown devices trigger an alert, and require tests to cover people, buildings and response time.
For brands planning a campaign
For a company assessing physical access and incident response, this is the strongest match in the examples.
A proposed exercise could test reception procedures, access to meeting rooms and network ports, and whether an alert reaches the right person quickly.
The post stresses written leadership approval and a report on what was and wasn’t detected.
How does John turn a service outage into a resilience question for a business?
Read more
This example shows how they connect a specific incident to practical preparation.
John compares card-payment outages caused by technical faults with a ransomware incident at a payment gateway.
For a shop, either can stop payments.
They ask readers to check whether terminals support offline payments, map the payment chain and decide in advance what to do during 48 hours without card payments.
For brands planning a campaign
Useful for a campaign about business continuity or third-party resilience. The post points to testing fallback procedures and mapping dependencies, rather than treating cybersecurity as only a matter of defending a network.
How does John make email authentication relevant to organizations whose messages can prompt urgent public action?
Read more
This post pairs a concrete scenario with steps for checking and improving protection.
John describes a false boil-water notice sent using a water utility’s name and reports that 663 of 798 examined water-utility domains lacked an instruction to reject spoofed mail.
They explain the roles of SPF, DKIM and DMARC, then recommend checking the domain, listing legitimate mail senders before changing DNS settings, and requesting a plan with a deadline.
They note that a domain count is not the same as a count of water utilities.
For brands planning a campaign
A strong example for a campaign about protecting trusted communications, especially in utilities or other public-facing services. It supports a practical sequence: assess domain settings, inventory sending systems, and set an accountable implementation date.
Does John write about resilience beyond cyberattacks?
Read more
This post shows them applying the same scrutiny to automated systems and the consequences of incorrect rules.
Using a reported error in the Danish Criminal Register, John explains how automated deletion rules can remove information too early or retain it too long.
They translate the issue into checks for businesses: list retention rules, test them with data that should be kept and deleted, and clarify how errors are handled.
They caution that a deletion log is not a copy of deleted data.
For brands planning a campaign
Relevant to campaigns about data governance, compliance or operational controls. It suggests a concrete exercise: test important retention rules against requirements and exceptions, then review evidence of the outcome.
Repeatable format: case, mechanism, three actions.9
Email authentication and domain spoofing, sector by sector5
Physical access and the limits of penetration testing1
Payment outages as an operational resilience problem1
Automated deletion and retention rules1
Sanctions, supplier dependence and digital sovereignty1
Email authentication and domain spoofing, sector by sector
Across several posts, John Nielsen measures whether Danish organisations prevent others from sending mail in their name.
Read more
Examples cover water utilities, municipal domains, agencies, audit and accounting firms, property administrators and hosting providers.
The posts explain SPF, DKIM and DMARC in plain terms, then give three practical steps: check the domain, list every system that sends mail, and ask for a dated plan to move DMARC to quarantine or reject.
The recurring point: a familiar sender name becomes a business risk when the domain owner has not instructed receiving mail systems what to do.
DNS-based sector benchmarking: measure domain records at scale, translate the results into concrete fraud or deliverability risks, and finish with a short checklist.
The figures show missing DMARC instructions, not that every named domain can be freely spoofed. Recipient mail filters still make the final decision.
For brands planning a campaign
This is a strong fit for brands selling email security, deliverability, fraud protection or managed IT to Danish decision-makers. Sector benchmarks offer specific hooks for sponsored analysis, co-created checklists or buyer-education content, provided the figures are current and independently checked.
Physical access and the limits of penetration testing
John Nielsen uses a first-person walkthrough to show how a visitor can pass reception, enter an empty meeting room and connect to the internal network through an unused port.
Read more
The post distinguishes three services buyers often confuse: a penetration test attacks selected technical systems; red teaming imitates a real attacker across technology, people and buildings; cyber security mystery shopping tests how far a friendly greeting gets someone. It cites Denmark's Nationalbank and the TIBER-DK programme as an existing model, then asks readers to count active network ports, check what happens when an unknown device connects, and require tests covering doors, people and response time.
First-person demonstration, clear service definitions and three operational checks.
For brands planning a campaign
This topic suits physical security, access-control, network-security and red-team providers. A campaign can use the walkthrough to educate buyers, paired with a checklist for reception, meeting rooms and network ports.
Payment outages as an operational resilience problem
Two Nets payment outages, in July 2025 and May 2026, frame a post about what happens when card payments stop.
Read more
John Nielsen notes that some shops could have taken offline card payments but did not use the option, and that the Financial Supervisory Authority later found weaknesses in IT risk management, crisis communication and tested exit plans.
The post compares a technical failure with the February 2026 BridgePay ransomware incident, then maps the payment chain from terminal supplier to gateway, acquirer, processor and subcontractors.
The practical advice: confirm offline payment capability, draw the chain and decide in advance what to do during 48 hours without card payments.
Incident comparison and dependency mapping, with a business-continuity checklist—not just a fraud warning.
For brands planning a campaign
Payment providers, insurers, retail-continuity services and IT resilience vendors can use this topic to reach operations and finance leaders. The post offers a clear scenario for campaigns about outage planning, supplier mapping and offline payment readiness.
A missing decision in Denmark's Criminal Register becomes a lesson in automated deletion.
Read more
John Nielsen explains that automatic routines removed records too early for some crime codes, a citizen's inquiry exposed the problem, and the rules depend on the right deadline, the right start date and correct handling of exceptions.
The post applies this to everyday systems: mail, ERP, document archives and CRM.
It gives three checks: list automated deletion rules and their legal basis; test the most important rule with data that should be kept, deleted or exempted; and clarify how deletions are logged and corrected.
Public-sector failure case followed by testable control questions for business systems.
For brands planning a campaign
Records-management, compliance, legal-tech and information-governance brands can use this topic. The case makes retention risk tangible for Danish organisations and supports campaign content about audits, testing and documented deletion controls.
Sanctions, supplier dependence and digital sovereignty
US sanctions against the International Criminal Court show how far legal exposure can travel through banks, insurers and software suppliers.
Read more
John Nielsen describes the court's earlier move to open-source office software, prepaid salaries and a replacement insurance provider after AXA ended cover.
The post also cites the 2022 collapse of Amsterdam Trade Bank and a Dutch request for an EU blocking regulation.
The advice: list mail, banking, payment and insurance suppliers alongside the laws that govern them; ask how each handles US sanctions; and decide which critical services need an alternative that cannot be hit by the same sanctions.
Geopolitical case study paired with a supplier-by-supplier dependency map.
For brands planning a campaign
Cloud-sovereignty, legal-compliance, insurance and supply-chain risk brands can use this topic. It gives campaigns a concrete frame for vendor concentration and the legal reach of foreign sanctions.
Repeatable format: case, mechanism, three actions.
The posts follow a consistent structure: John Nielsen opens with a specific incident or measurement, explains the mechanism, gives three numbered actions and closes with a question and an invitation to a fortnightly newsletter.
Read more
They use named sources and exact figures, and several distinguish hypothetical examples from the real mechanisms they explain. The format favors reportage and explanation over personal opinion, while remaining scannable for LinkedIn readers.
Case-led explainer with numbered actions and a closing reader question.
Some scenarios are explicitly hypothetical and explain a real mechanism. Do not present them as reported incidents.
For brands planning a campaign
This format suits co-created explainers or sponsored checklists, but the brand must supply verifiable data and legal or technical review. Preserve the case anchor and practical sequence rather than turning the post into a generic brand message.
John Nielsen's posts name no sponsor, affiliate, or client brand.
Read more
The clear commercial presence is their own DMARC work: they describe a free mail checker and a DMARC barometer as theirs, and use their findings as the basis for their posts.
They also write about doing penetration tests at customers, but name no client or employer.
Companies such as Nets, Microsoft and AXA appear as case subjects, not as disclosed relationships.
Ask for named client or employer references if those relationships matter to your decision.
DMARC-tjek.dk
Owned business
Nielsen calls the free DMARC checker “mit gratis mailtjek” and directs readers to dmarc-tjek.dk for a prioritised report.
Nielsen refers to the figures as “Tallene fra mit barometer” and links readers to dmarc-barometer.dk.
Read more
Elsewhere, they say they analysed hundreds of thousands of domains from the barometer’s dataset. The posts show them operating or fronting the project.
Start with the sector measurements on email authentication: they show how John Nielsen takes a familiar sender name, measures whether the domain owner tells receiving systems to reject impostors, then turns the gap into a short management checklist.
Read more
Next, read the front-door walkthrough to see how they distinguish penetration testing, red teaming and mystery shopping; the payment-outage and supplier-sanctions posts to see how they map operational dependencies; and the Criminal Register post to see the same test applied to automated deletion rules. The through-line is named ownership and a testable answer before an incident forces the question.
Both treat third-party dependency as a resilience problem.
Read more
Stefan Kløvning's Cloudflare outage post warns about single points of failure and calls for risk mapping, backups and crisis protocols; John Nielsen's payment and sanctions posts trace the same exposure through terminal suppliers, banks, insurers and software providers.
Kløvning's integration post is a buyer's guide to no-code, low-code and full-code choices. Nielsen's work examines security and continuity through domain control, physical access and payment outages.
Both write for Danish commercial leaders about technology governance in business language.
Read more
Christian Lunøe Gøtzsche's posts turn AI agent architecture and EU AI Act and GDPR compliance into operational questions; Nielsen's turn email authentication, security testing and supplier exposure into management checklists.
Gøtzsche focuses on AI adoption, agent workflows and compliance training. Nielsen focuses on cyber security controls, fraud prevention and operational continuity.
Both give practical, first-person advice to Danish business readers about adopting technology.
Read more
Micky Weis describes an AI stack and Q4 e-commerce preparation; Nielsen describes domain checks and security tests.
Weis covers e-commerce growth and marketing operations; Nielsen covers cyber security and resilience. Readers following Weis for AI tooling won't get Nielsen's security-testing depth, and vice versa.
For a campaign targeting Danish mid-sized-company decision-makers or security staff, John Nielsen’s posts establish topical relevance as a Danish-language cybersecurity voice, but not access to either audience segment.
Read more
The account has 26,159 LinkedIn followers as of 9 October 2026.
Posts repeatedly cover topics relevant to the campaign, including network access control, penetration testing and red teaming, incident response, email and domain protection, and supplier resilience.
They provide no breakdown by employer size, job title, occupation, or seniority, so the number of Danish mid-sized-company decision-makers or security staff among the followers is unknown.
Treat the account as a candidate for broad Danish security and business reach, and request a recent audience survey or platform demographics report showing geography, age, gender and, if available, role or company size.
Before committing to a penetration testing or red teaming angle, also request recent performance data for posts on those topics at comparable depth.
LinkedIn followers
26,159
LinkedIn account snapshot for John Nielsen · 2026-10-09
John Nielsen's posts contain no published partnership or sponsorship formats.
Read more
The nine posts are cybersecurity commentary and advisory writing in Nielsen's own voice; none is labelled as sponsored, and no media kit, rate card, deliverable list, or sponsor policy appears in the posts here.
The one recurring commercial element is a subscription link at the end of every post, inviting readers to a newsletter Nielsen describes as reaching "4,400+" subscribers with patterns from "500+ cases" and recommendations on digital sovereignty and cybersecurity every 14 days.
That is Nielsen's own audience channel, not a documented brand offer, and the subscription terms and audience figures are Nielsen's own stated claims rather than figures verified elsewhere.
Because the posts set out no formats, pricing, approval steps, or usage rights, a buyer cannot plan deliverables or budget from the information published here; any collaboration would have to be scoped in direct negotiation, and those terms remain unverified.
The post about network access control shows Nielsen performs penetration tests, red teaming exercises, and security mystery shopping for clients, which indicates the kind of professional engagement Nielsen does, but it is not presented as a creator partnership offering and carries no commercial specifications.
A reasonable planning assumption is that a brand approaching Nielsen is buying access to the professional audience through a practitioner who writes from client work, and that the practical constraints — what Nielsen will endorse, how work is labelled, and what Nielsen charges — are unknown until discussed with Nielsen.
The posts here do not document sponsorship; that does not mean Nielsen never accepts sponsorship.
Need: A mid-sized Danish company wants to improve its cyber security posture and resilience.
Read more
It is considering a penetration test and red teaming exercise to evaluate network access control and incident response.
Decision: Strong topical fit for an editorially led, Danish-language B2B campaign, provided the brand scopes the engagement directly with John Nielsen and checks the audience before booking.
Reasons: In the posts, John Nielsen writes as a practitioner about authorized entry through reception into an empty meeting room and an unused network port; separates penetration testing, red teaming and cyber security mystery shopping; cites Denmark's TIBER-DK programme; and gives three operational checks: count active network ports and close unused ones, ask what happens when an unknown device connects and how fast an alert reaches the right person, and require tests covering doors, people and response time.
That maps closely to the company's network access control and incident response needs.
The wider work on payment outages, DMARC and supplier dependence also supports a resilience narrative.
Limits: the posts do not establish that John Nielsen's audience contains buyers for this campaign; no employer size, role or seniority data is published.
No sponsorship formats, rates or approval terms are published in the posts here.
This is topic and credibility fit, not verified audience fit or a ready-made media buy.
When to choose a specialist
Need: A Danish consumer payments app wants a lifestyle creator campaign to drive mass consumer downloads among urban 25-40 users, using short-form video, discount codes and everyday spending content.
Read more
Decision: Poor fit for this campaign.
Reasons: John Nielsen's work is Danish-language B2B cybersecurity advisory, not consumer lifestyle or app-promotion content.
The payment-outage post is about business continuity for shops and operations leaders: offline terminals, payment-chain mapping and 48-hour fallback.
It is not consumer acquisition, personal finance or lifestyle video.
The posts here do not show short-form video, discount-code promotion or consumer product demonstration.
The posts also do not establish audience composition; follower count alone cannot show reach among the target consumer group.
Commercial format is absent: no published media kit, rate card or sponsorship terms means the brand cannot plan deliverables or budget from published information.
The topic overlap with payments is not enough to recommend this creator for a mass consumer campaign; a payments-adjacent message would still need a B2B or operational buyer and a directly negotiated campaign scope.
A worked campaign example
Worked angle for the good-fit brief: 'The front-door test'.
Proposition: a firewall does not stop someone who is already in the meeting room.
Use John Nielsen's authorized walkthrough as the anchor.
Audience: Danish mid-sized-company leaders in security, IT operations and risk, plus operations or finance leaders responsible for resilience.
Format: a sponsored, clearly labelled written explainer in their case-mechanism-three-actions style, followed by a one-page access-control checklist for reception, meeting rooms and active network ports.
The explainer opens with the contrast between the hooded-hacker image and the calm visitor with a bag; explains that the test was agreed with management and documented; defines penetration test, red team and mystery shopping; then asks the buyer to count active ports, test unknown-device alerts and measure response time.
Brand role: if the sponsor sells network access control or incident-response services, it supplies product facts and a demo route, while John Nielsen keeps the editorial framing and the report language.
Sequence: week 1 publish the explainer; week 2 publish the checklist and a written leadership briefing; week 3 run a scoped debrief where the buyer walks through what was and was not detected.
Call to action: request a written, leadership-approved front-door exercise brief and a report showing detection time.
Measure: checklist downloads, brief requests and debrief attendance rather than impressions alone.
This is a proposed campaign angle, not a documented sponsorship package; agree format, price, labelling and approval steps directly.
A better fit than John Nielsen only if the buyer reframes resilience around AI governance: how commercial teams use AI agents, where data sits, and how EU AI Act and GDPR guardrails are built into workflows.
Read more
The posts show a commercial leader testing an autonomous agent workflow for a B2B company and arguing that governance should provide strategic guardrails, not act as a bureaucratic brake. For a mid-sized Danish company whose immediate risk is ungoverned AI use in sales or marketing, this is the more direct content fit.
The posts offer no evidence of penetration testing, red teaming, network access control or incident-response exercises. This creator offers AI governance and commercial adoption framing rather than offensive security expertise; buyers should seek a separate security tester for front-door and detection work.
A better fit when the buyer's cyber resilience question is really about operational readiness in e-commerce: email and customer flows, Q4 preparation, content production and using AI on first-party data.
Read more
The posts offer concrete checklists for flows, branding, onsite merchandising and data analysis. For a Danish e-commerce business whose continuity risk lies in customer communication and trading readiness, Micky Weis offers more directly usable campaign material than Nielsen's security-testing posts.
The posts offer no evidence of penetration testing, red teaming, network access control or incident-response testing.
They provide growth and operations advice, not security assurance.
A campaign focused on security testing would need a security specialist alongside this creator; e-commerce readiness is no substitute for a front-door test.
A better fit when the buyer's resilience decision concerns system integration and third-party dependency: how CRM and finance systems connect, and what happens when a shared platform fails.
Read more
The Cloudflare post identifies single points of failure and recommends mapping risks, backups, crisis protocols and training; the integration post explains when no-code, low-code or full-code fits. For a mid-sized Danish company worried about supplier concentration and continuity, this is closer to the operational resilience question than John Nielsen's testing-focused material.
The integration advice covers architecture and continuity, not offensive security testing.
The posts are in Norwegian and English, while Nielsen's are in Danish, so a Danish-language campaign needs a language plan or translation.
This creator offers system-dependency analysis rather than hands-on security testing; buyers should pair the content with a security specialist if testing is the priority.
John Nielsen's nine LinkedIn posts, published 9 September to 9 October 2026, discuss events and measurements from July 2025 to October 2026.
The page's overview, ideas, relationships, discovery and fit sections are also available.
The posts cover email authentication and domain spoofing, penetration testing and red teaming, payment outages, automated data deletion, and supplier or sanctions exposure.
This is not a full lifetime archive: no long-form articles, talks, audience demographics or published sponsorship terms appear in the posts here.
Claims are limited to what the posts show; the posts do not independently verify employers and credentials.