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normSight — Cyber Security

23 September 2026

Data breach notification: managing the 72-hour window

The notification window starts the moment a breach becomes known; managing it depends on having a response plan, available evidence sources and a designated decision-maker in place beforehand.

Plenty of organisations know they have a breach notification obligation. Far fewer are in a position to meet it.

The difference comes down to one thing: the clock starts the moment you learn of the breach, and by then there is no time left to prepare.

Where the hours go

In an unprepared organisation the sequence typically runs like this:

HourWhat actually happens
0–6Debate over whether this is really a breach. Nobody is clearly the decision-maker.
6–18Hunting for logs. Discovering some were never collected.
18–36Trying to establish scope: what data, how many people, what date range.
36–60Legal and management step in; the notification wording is debated.
60–72A notification is assembled in a hurry, with incomplete information.

Actual technical investigation in that sequence gets a few hours. The rest is organisational delay — and all of it can be removed in advance.

Four things to settle before the clock starts

1. Who decides

Who determines whether an event counts as a breach must be written down in advance, along with who takes over if that person is unreachable. Where the decision-maker is unclear, the first hours go to debate.

2. Where the evidence comes from

The sources needed for an investigation must already exist at the moment of the breach:

  • Authentication and authorisation logs
  • Database access logs
  • Web server access logs
  • Endpoint telemetry
  • Network flow records

How far back they reach matters just as much. If the attacker got in three months ago and your logs are kept for two weeks, you cannot establish scope — and when you cannot establish scope, you have to assume the worst case.

3. What the notification will say

The information a notification must carry is known: the nature of the breach, the approximate number of people and records affected, its likely consequences, and the measures taken and planned.

A template for those headings can be prepared in advance. Text first drafted during a breach is not good text.

4. Who investigates

If the organisation has no forensic capability in-house, the external firm must be selected in advance with a contract already in place. Sourcing a supplier and negotiating terms on the day consumes half the window.

The most expensive mistake: destroying the evidence

In unprepared organisations the first reflex is usually to restore service fast: the affected server is rebuilt, disks are wiped, the service is restarted.

The consequence is that you will never learn what happened. Evidence in memory is lost, deleted files are overwritten, the attacker’s traces disappear. Unable to establish scope, you end up writing “the number of affected individuals could not be determined” — which is itself read as evidence of inadequate measures.

The correct order is: image first, then respond. No system should be rebuilt before disk and memory images are taken. This belongs as the first line of the incident response plan.

The ransomware case

Most ransomware operations now exfiltrate data before encrypting it. The incident is therefore not only an availability problem but a probable confidentiality breach.

The practical consequence: work on the assumption of exfiltration until proven otherwise. A judgement of “it was only encrypted, nothing left” cannot be made without examining outbound network traffic.

Testing the plan

A response plan that has been written but never exercised is only slightly better than none. A table-top exercise closes that gap: a scenario is given, the team walks through what it would do, and the gaps surface.

Typical findings from an exercise: the decision-maker was in fact undefined, a critical system logs nothing, restoring from backup takes three times the estimate, two people on the contact list have left.

Learning those things on the day of a breach is expensive.

Building the capability

Incident response is not something to improvise. Team, process and tooling have to be in place beforehand.

normSight’s CSIRT / Incident Response training targets exactly this: establishing the response process, detection, containment and safe recovery. For the evidence side see Digital Forensics, and for proactively hunting undetected adversaries, Cyber Threat Hunting.

The wider set of compliance obligations is covered in KVKK compliance.

This article is general information and does not constitute legal advice. For notification deadlines, content and recipients specific to your organisation, consult your legal counsel.

  • data breach
  • incident response
  • KVKK
  • CSIRT

Frequently Asked Questions

When does the clock start?

Not when the breach occurred, but when the data controller becomes aware of it. Detection capability therefore directly affects your exposure: if you notice a months-long leak today, the window starts today — but having failed to detect it for months is itself a shortfall in measures that will be assessed separately.

Should we notify even if we do not yet know exactly what happened?

Yes. Notification does not wait for the investigation to conclude. You notify with what is known and update as the investigation progresses. Spending the window gathering certainty breaches the obligation without improving the outcome.

Does a ransomware attack count as a data breach?

Even where data was only encrypted and not taken, there is a loss of availability that requires assessment. Because most current ransomware operations exfiltrate data before encrypting, it is safer to work on the assumption of exfiltration until proven otherwise.

Do we also have to notify the individuals affected?

Notification to affected individuals is required. Its content and timing are assessed according to the nature of the breach and the risk it creates for those individuals.

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