By Maryne Robin, MBA, ITIL, CISSP – expert in cybersecurity, compliance, and IT risk management

Hour 0–24: Confirm the Incident, Contain the Threat, Understand the Scope

During the first two hours, the priority is confirming the incident and containing the immediate threat. Determining the full scope typically continues throughout the rest of the first 24 hours.

How Do You Confirm a Cybersecurity Incident?

Not every security alert is an active breach. Security teams often begin by separating routine noise from genuine malicious activity. For example, an employee logging in from an unfamiliar location might simply be traveling. But when unusual login activity is followed by unexpected account behavior, suspicious network connections, or attempts to access systems outside that user’s normal role, responders begin treating the activity as a potential compromise.

Once responders determine they’re dealing with an active incident, the organization’s incident response plan (IRP) should be activated immediately. In the earliest hours of an incident, delaying action while waiting for complete certainty often gives attackers additional time to expand their access, move laterally across the network, or steal sensitive data.

What Gets Contained First?

Effective containment balances two competing priorities: limiting the attacker’s access while maintaining business operations wherever it can be done safely. During these initial hours, the goal is to interrupt the attack as quickly as possible without creating unnecessary disruption.

Depending on the situation, responders may isolate compromised endpoints from the network, disable affected user accounts, revoke privileged sessions, or block known malicious IP addresses. Organizations using security orchestration, automation, and response (SOAR) can automate many of these initial containment actions through predefined playbooks, helping security teams isolate compromised devices, disable accounts, and block malicious activity within seconds while analysts continue investigating.

One mistake organizations frequently make is restoring systems too early. If the attacker still maintains access through an overlooked account, scheduled task, remote management tool, or stolen credentials, the compromise can quickly begin again.

How Do You Determine the Scope of the Breach?

The first identified compromised system is rarely the only one. Security teams immediately begin asking questions that determine the scale of the incident:

• Which systems have been affected?
• Has sensitive or regulated data been accessed?
• Is the attacker still active?
• How did they move through the environment?
• Which business services are now at risk?

At the same time, responders begin preserving forensic evidence. Firewall logs, endpoint telemetry, authentication records, cloud activity, and memory captures can later explain exactly how the attacker gained access. Losing that evidence can make root cause analysis – and sometimes regulatory reporting – far more difficult.

Hour 24–48: Investigate the Attack and Coordinate the Response

Once immediate containment measures are in place, investigators begin reconstructing how the compromise occurred and whether any attacker access remains.

How Do Security Teams Identify the Root Cause?

Experienced responders work backward from the evidence to identify the initial point of compromise. Removing malware alone rarely solves the problem if the original access path remains open. The compromise may have started with a phishing email that captured an employee’s credentials, an unpatched VPN appliance, compromised third-party credentials, or an unsecured remote access tool.

Reconstructing the attack timeline often uncovers additional compromised systems, dormant persistence mechanisms, or evidence that attackers spent days (or weeks) inside the environment before being detected. Finding and eliminating the original point of compromise is just as important as removing the visible symptoms.

Who Should Be Involved During an Incident?

Decisions made during an incident extend well beyond the security team. Executive leadership, legal counsel, compliance, operations, communications, and external partners often need to make coordinated decisions within hours.

While technical teams focus on containment, leadership needs accurate information about operational impact, customer risk, regulatory obligations, and recovery timelines. Frequent, evidence-based updates help organizations make informed decisions instead of reacting to rumors or incomplete information.

When Do Compliance and Regulatory Requirements Apply?

For organizations in regulated industries, incident response includes more than technical recovery. Financial institutions face industry-specific reporting obligations. Organizations supporting government agencies or defense contractors may have contractual reporting timelines that begin almost immediately after confirming an incident. Healthcare organizations may need to evaluate HIPAA breach notification requirements.

Compliance should never be treated as a separate workstream. Legal obligations, forensic investigation, documentation, and technical response all happen simultaneously.

Hour 48–72: Remove the Threat and Begin Safe Recovery

By this point, organizations typically understand the attack well enough to begin eliminating it completely.

How Do You Remove an Attacker Completely?

Before systems are restored, responders must be confident that attacker access has been eliminated and exploited vulnerabilities have been addressed. That includes removing persistence mechanisms, revoking compromised credentials, rotating passwords, patching exploited vulnerabilities, strengthening privileged access controls, and verifying that malicious software has been fully eradicated.

Endpoint detection and response (EDR), managed detection and response (MDR), and security information and event management (SIEM) platforms provide the visibility needed to confirm that malicious activity has stopped rather than simply become less visible.

When Is It Safe to Restore Systems?

Restoring systems too quickly is one of the costliest mistakes organizations can make. Before systems return to production, responders need confidence that backups are clean, vulnerabilities have been addressed, compromised accounts have been secured, and monitoring has been strengthened. Otherwise, recovery becomes an opportunity for attackers to regain access.

Recovery should be prioritized based on business impact. Identity services, communication platforms, financial systems, electronic health records, and other business-critical applications typically take precedence over less critical workloads.

What Should Organizations Learn Before Closing the Incident?

The incident isn’t truly over when systems come back online. Every cybersecurity incident provides insight into security gaps that previously went unnoticed. Maybe privileged accounts had excessive permissions. Maybe endpoint visibility was incomplete. Maybe phishing-resistant multifactor authentication wasn’t fully deployed.

Four Mistakes That Consistently Slow Recovery

1. Waiting too long to contain the threat. Organizations sometimes delay action while trying to gather more information. Unfortunately, attackers rarely pause while investigations catch up.
2. Destroying valuable forensic evidence. Reimaging devices, deleting logs, or shutting down compromised systems before investigators have collected evidence can erase valuable forensic data – including information stored only in volatile memory – making it much harder to determine what happened, how far the compromise spread, or whether regulatory reporting requirements apply.
3. Treating incident response as an IT-only problem. Executive leadership, legal counsel, compliance teams, communications, and business operations all play critical roles in successful incident response.
4. Stopping once systems are restored. Recovery without understanding the root cause can leave the door open for the next attack.

ABOUT THE AUTHOR

Maryne Robin, Manager of Security and Compliance at Omega Systems, leads the SOC team and oversees key security services, including managed detection and response, IT compliance, and network security. A CISSP-certified professional with 20+ years in IT and cybersecurity, she specializes in compliance and proactive risk management.

Connect with Maryne on LinkedIn.