A cybersecurity incident can begin with something as simple as a suspicious email, an unusual login, an unexpected system alert, or an employee reporting that their computer is behaving strangely.
Within hours, what appears to be a minor security issue could develop into ransomware, data theft, account compromise, or widespread disruption across the organisation.
When an incident occurs, the first 24 hours are critical.
The actions your organisation takes during this period can determine how quickly the threat is contained, how much damage is caused, and how effectively normal operations can be restored.
Yet many organisations are unsure what to do when a real incident happens.
Who should be contacted first? Should the affected device be shut down? Should employees be informed? How do you determine whether sensitive data has been compromised?
This is why having a structured incident response process before an attack occurs is essential.
Here is what organisations should focus on during the first 24 hours of a cybersecurity incident.
1. First Few Hours: Identify and Verify the Incident
Not every security alert means your organisation has suffered a breach. However, unusual activity should never be ignored.
The first priority is to determine what has happened and how serious the situation may be.
Security and IT teams should begin collecting information about the incident, including:
- When the suspicious activity was first detected
- Which users, accounts, devices or systems may be affected
- What security alerts or unusual behaviours were observed
- Whether sensitive or critical systems are involved
- Whether there are signs of malware, ransomware or unauthorised access
- Whether the suspicious activity is continuing
At this stage, avoid making assumptions based on a single alert.
Security logs from endpoints, servers, firewalls, identity systems, cloud platforms and other security tools may need to be correlated to understand what is actually happening.
The objective is to establish an initial picture of the incident and determine the appropriate level of response.
2. Contain the Threat Before It Spreads
Once an incident has been identified, containment becomes one of the most important priorities.
Attackers who gain access to one system may attempt to move laterally through the network, compromise additional accounts, escalate privileges or access sensitive information.
Depending on the incident, containment measures could include:
- Isolating compromised endpoints or servers from the network
- Disabling or restricting compromised user accounts
- Blocking malicious IP addresses, domains or indicators of compromise
- Revoking suspicious active sessions
- Resetting affected credentials
- Restricting access to critical systems
- Temporarily disabling compromised services or applications
However, containment should be handled carefully.
Immediately deleting files, wiping devices, or making uncontrolled changes could destroy valuable evidence that investigators need to understand how the attack occurred.
Where possible, preserve relevant logs, system information, and other evidence before making significant changes.
The goal is simple: stop the attacker from causing further damage while preserving enough evidence to investigate what happened.
3. Investigate the Scope and Preserve Evidence
Containing an affected computer does not necessarily mean the incident is over.
An attacker may have already accessed other systems before the original compromise was discovered.
The next step is to determine the full scope of the attack.
The investigation should attempt to answer several important questions:
- How did the attacker gain initial access?
- Which accounts were compromised?
- What systems did the attacker access?
- Did the attacker obtain administrative privileges?
- Was malware installed?
- Did lateral movement occur?
- Was sensitive information accessed or exfiltrated?
- Are there additional compromised systems that have not yet been detected?
- Is the attacker still present within the environment?
This is where digital forensics, log analysis, endpoint telemetry and threat hunting can become extremely valuable.
Organisations should also preserve relevant evidence such as authentication logs, endpoint data, firewall logs, email records and cloud activity logs.
Good evidence preservation helps security teams reconstruct the attack timeline and determine the true extent of the incident.
4. Activate Your Incident Response and Communication Plan
Cybersecurity incidents are not purely technical problems.
A serious incident may require coordination across multiple parts of the organisation, including management, IT, cybersecurity, legal, compliance, communications and business operations.
An organisation’s incident response plan should clearly define who needs to be involved and who has authority to make critical decisions.
During the first 24 hours, organisations should consider:
- Activating the internal incident response team
- Escalating the incident to senior management where appropriate
- Informing legal, risk and compliance teams
- Documenting decisions and actions taken during the response
- Determining whether customers, partners or other stakeholders may be affected
- Assessing applicable regulatory or contractual reporting obligations
- Preparing controlled internal or external communications if required
Communication should be accurate and coordinated.
Sharing incomplete or unverified information too early can create unnecessary confusion. At the same time, delaying necessary escalation can make the incident harder to manage.
Having predefined communication procedures helps organisations respond more effectively under pressure.
5. Prepare for Recovery — But Don’t Rush Back Online
After the immediate threat has been contained and investigated, attention can begin shifting toward recovery.
However, restoring systems too quickly without addressing the original cause can allow the attacker to regain access.
Before returning affected systems to normal operations, organisations should consider:
- Removing malicious files, persistence mechanisms and unauthorised accounts
- Patching exploited vulnerabilities
- Resetting compromised passwords and credentials
- Reviewing privileged access
- Restoring systems from known-clean backups where necessary
- Verifying that restored systems are secure
- Increasing monitoring for suspicious activity
- Confirming that the attacker no longer has access
Recovery should be controlled and prioritised according to business criticality.
Critical systems may need to be restored first, while affected systems should continue to receive enhanced monitoring for signs of reinfection or renewed attacker activity.
Preparation Before an Incident Makes the Biggest Difference
The worst time to create an incident response plan is during an actual cyberattack.
Organisations should prepare before an incident occurs by establishing clear responsibilities, escalation procedures and technical response processes.
Preparation can include:
- Maintaining an updated incident response plan
- Clearly defining incident response roles
- Conducting tabletop exercises and simulations
- Ensuring security logs are available and retained
- Maintaining secure and tested backups
- Monitoring critical systems continuously
- Keeping an up-to-date inventory of systems and assets
- Establishing relationships with external cybersecurity and forensic specialists
Regular exercises are particularly valuable because they allow organisations to identify gaps in their response process before those gaps are exposed during a real attack.
Conclusion: The First 24 Hours Can Shape the Entire Incident
Cyber incidents are stressful, fast-moving and often unpredictable.
But organisations do not need to respond blindly.
The first 24 hours should focus on five priorities:
Identify → Contain → Investigate → Communicate → Recover
Identify what happened and determine the severity. Contain the threat before it spreads. Investigate the full scope of the compromise and preserve evidence. Coordinate communication and escalation across the organisation. Finally, begin a controlled recovery once the environment is safe.
Most importantly, incident response should not begin when an attack happens.
The organisations that respond most effectively are usually those that have already established the people, processes and technology needed to handle an incident before one occurs.
Is Your Organisation Prepared for a Cyber Incident?
Knowing what to do during the first 24 hours can make a significant difference in minimising business disruption, containing threats and reducing the overall impact of a cybersecurity incident.
Being prepared starts with having the right cybersecurity measures in place.
Condition Zebra helps organisations strengthen their cybersecurity posture, improve threat detection capabilities and build cyber resilience through a comprehensive range of cybersecurity services, including:
- Vulnerability Assessment & Penetration Testing (VAPT) – Identify and address security weaknesses before attackers can exploit them.
- Managed Detection & Response (MDR) – Continuously monitor, detect and respond to potential cyber threats.
- Security Awareness Training – Equip employees with the knowledge to recognise and respond to cybersecurity threats.
- Cybersecurity Training (Online or In-Person) – Build practical cybersecurity skills and strengthen your team’s ability to manage security risks.
📩 Contact us for a FREE consultation to discuss your organisation’s cybersecurity readiness and identify areas that may need strengthening.