Incident Response: The Critical First 24 Hours

The average time to identify a data breach is 204 days. But when a breach is detected, the first 24 hours determine whether the damage is contained or catastrophic. Having a clear, practised incident response plan is the difference between a manageable event and a business-ending crisis.

Before an Incident: Preparation

The best time to prepare for an incident is before it happens. Ensure you have:

• An incident response plan documented and accessible to all relevant staff
• Defined roles and responsibilities — who leads, who communicates, who contains
• Contact lists for key personnel, legal counsel, law enforcement, and regulators
• Regular tabletop exercises to practise the plan
• Logging and monitoring in place to support investigation

Hour 0–2: Detection and Initial Assessment

Confirm the Incident

Not every alert is a real incident. The first step is to determine:

• Is this a genuine security event or a false positive?
• What systems or data are affected?
• Is the attack still active?

Activate the Response Team

Notify the designated incident response lead and assemble the core team:

• IT / Security lead
• Communications / PR
• Legal counsel
• Senior management representative
• Data Protection Officer (if personal data may be affected)

Preserve Evidence

• Do not turn off affected systems unless necessary to stop ongoing damage. Powering down can destroy volatile evidence (memory, network connections).
• Begin logging all actions taken, decisions made, and their timestamps.
• Capture screenshots, logs, and network traffic where possible.

Hour 2–8: Containment

Short-term Containment

The immediate priority is stopping the attack from spreading:

• Isolate affected systems from the network
• Block compromised accounts
• Implement temporary firewall rules
• Change credentials for affected services

Assess the Scope

• How many systems are affected?
• What data has been accessed, exfiltrated, or encrypted?
• Are backups intact and uncompromised?
• Is the attacker still present in the environment?

Hour 8–16: Eradication and Recovery Planning

Remove the Threat

• Identify and remove malware, backdoors, or compromised accounts
• Patch the vulnerability that was exploited
• Verify that all attacker access has been revoked

Plan Recovery

• Determine the order of system restoration based on business priority
• Verify backup integrity before restoring
• Plan for enhanced monitoring during recovery

Hour 16–24: Communication and Reporting

Internal Communication

• Brief senior leadership with a clear summary: what happened, what was affected, what has been done
• Update all staff with appropriate information (without revealing sensitive details that could aid attackers)

Regulatory Notification

If personal data has been compromised:

• GDPR requires notification to the supervisory authority within 72 hours
• Prepare the notification with details of the breach, likely consequences, and measures taken
• Determine whether affected individuals need to be notified

External Communication

• Prepare a holding statement for media enquiries
• Do not speculate about the cause or scope publicly
• Be transparent but measured — premature blame or detail can cause additional harm

After the First 24 Hours

The initial response is just the beginning. In the following days and weeks:

• Complete a thorough forensic investigation
• Implement long-term fixes for the exploited vulnerabilities
• Conduct a post-incident review (blameless retrospective)
• Update the incident response plan based on lessons learned
• Provide additional training to prevent recurrence

Conclusion

Every organisation will face a security incident at some point. The question is not if, but when. A well-rehearsed incident response plan ensures that when the moment comes, your team acts with clarity and purpose rather than panic. Regular training and simulation exercises are the best investment you can make in incident preparedness.