--- title: What Happens in the First 24 Hours of a Cyberattack? description: Learn the critical steps that occur in the first 24 hours of a cyberattack and how to prepare your business for an effective response. image: https://blog.yournucleus.ca/hubfs/Cyber%20Insurance%20Is%20Changing%20%20Is%20Your%20Business%20Ready%20to%20Renew%20(1).png --- [Skip to content](https://blog.yournucleus.ca/what-happens-in-the-first-24-hours-of-a-cyberattack#main-content) [![Nuc-logo-sketched-1 (1)](https://blog.yournucleus.ca/hs-fs/hubfs/nucleus-images/Nuc-logo-sketched-1%20(1).png?width=220&height=44&name=Nuc-logo-sketched-1%20(1).png "Nuc-logo-sketched-1 (1)")](https://yournucleus.ca) - About Show submenu for About ![](https://blog.yournucleus.ca/hubfs/nucleus-images/caret.png) - [About Nucleus](https://yournucleus.ca/about/) - [Careers](https://yournucleus.ca/careers/) - [History](https://yournucleus.ca/about/history/) - [Team](https://yournucleus.ca/about/team/) - Services Show submenu for Services ![](https://blog.yournucleus.ca/hubfs/nucleus-images/caret.png) - [Managed IT Support](https://yournucleus.ca/services/managed-it-support/) - [Cybersecurity Services](https://yournucleus.ca/services/cybersecurity-services/) - [Managed AI Solutions](https://yournucleus.ca/services/managed-ai-solutions/) - [IT Consulting](https://yournucleus.ca/services/it-consulting/) - [Microsoft 365](https://yournucleus.ca/services/microsoft-365/) - [vCIO](https://yournucleus.ca/services/vcio/) - [ALL](https://yournucleus.ca/services/) - Results Show submenu for Results ![](https://blog.yournucleus.ca/hubfs/nucleus-images/caret.png) - [Architecture](https://yournucleus.ca/results/architecture-engineering-construction/) - [Legal](https://yournucleus.ca/results/legal/) - [Mining](https://yournucleus.ca/results/mining/) - [All](https://yournucleus.ca/results/) - [Blog](https://blog.yournucleus.ca) - About Show submenu for About ![](https://blog.yournucleus.ca/hubfs/nucleus-images/caret.png) - [About Nucleus](https://yournucleus.ca/about/) - [Careers](https://yournucleus.ca/careers/) - [History](https://yournucleus.ca/about/history/) - [Team](https://yournucleus.ca/about/team/) - Services Show submenu for Services ![](https://blog.yournucleus.ca/hubfs/nucleus-images/caret.png) - [Managed IT Support](https://yournucleus.ca/services/managed-it-support/) - [Cybersecurity Services](https://yournucleus.ca/services/cybersecurity-services/) - [Managed AI Solutions](https://yournucleus.ca/services/managed-ai-solutions/) - [IT Consulting](https://yournucleus.ca/services/it-consulting/) - [Microsoft 365](https://yournucleus.ca/services/microsoft-365/) - [vCIO](https://yournucleus.ca/services/vcio/) - [ALL](https://yournucleus.ca/services/) - Results Show submenu for Results ![](https://blog.yournucleus.ca/hubfs/nucleus-images/caret.png) - [Architecture](https://yournucleus.ca/results/architecture-engineering-construction/) - [Legal](https://yournucleus.ca/results/legal/) - [Mining](https://yournucleus.ca/results/mining/) - [All](https://yournucleus.ca/results/) - [Blog](https://blog.yournucleus.ca) [Contact](https://yournucleus.ca/contact/) [1-844-301-HELP](tel:1-844-301-4357) # What Happens in the First 24 Hours of a Cyberattack? October 13, 2026   |  [Security](https://blog.yournucleus.ca/tag/security),   [IT Support](https://blog.yournucleus.ca/tag/it-support) A security alert appears. An employee suddenly can't access files. Someone notices activity in an account they don't recognize. At first, nobody may know if the problem involves one device or a much larger part of the network. Decisions made during the hours that follow influence how far an incident spreads, how much of the business is disrupted, and what recovery looks like. IT teams may be investigating and containing the threat while leadership assesses business impact, and employees wait for direction. Every cyber incident unfolds differently, so there is no universal 24-hour schedule. Understanding what typically happens during the early response allows businesses to prepare before they find themselves in one. ### **Hour 0: Something Isn't Right** Cyber incident detection might begin with a security alert, unusual network activity, an employee reporting a suspicious login, inaccessible files, or a notification from a vendor or security provider. An initial warning doesn't necessarily reveal what happened or how far the problem extends. The priority is to establish what is known and bring in the people responsible for investigating. Employees should know where to report suspicious activity. Trying to fix the problem independently, deleting files, or making unplanned changes to affected systems interferes with the response. ### **Hours 1–4: Contain the Threat** Once an incident has been identified, attention turns to limiting its reach. The appropriate response depends on the attack. Security teams may isolate affected devices, disable compromised accounts, block malicious access, restrict network connections, or take selected systems offline. Containment requires care. Restoring normal operations too quickly can allow malicious activity to continue, while indiscriminate changes can remove information investigators need to determine what happened. Responders also begin documenting the incident. Recording when activity was detected, which systems or accounts were affected, and what actions have been taken creates a timeline that can support the investigation and decisions that follow. ### **Hours 2–6: Bring in the Right People** Technical response is only part of the work. Leadership, IT and security teams, legal or privacy advisers, communications staff, cyber insurance contacts, and external specialists may have roles depending on the nature and scope of the incident. Several decisions can emerge quickly. Someone needs authority to approve operational changes. Employees need instructions. Insurance requirements may need to be reviewed. Legal and privacy obligations may need attention. Incident response doesn’t progress in neat stages, so these conversations happen while containment and investigation are still underway. Knowing who owns each responsibility before an incident saves valuable time when multiple teams need to act at once. ### **Hours 4–12: Assess the Business Impact** As investigators learn more about the incident, leadership needs to understand how it is affecting operations. Which systems are unavailable? Can employees continue working? Are customer-facing services affected? What functions need to return first? Recovery priorities become important here. A business-critical application may need attention before a secondary system, even if both were affected by the same incident. [Business continuity planning](https://blog.yournucleus.ca/business-continuity-and-disaster-recovery) gives the response team an established order to work from. Critical systems, operational dependencies, and alternative ways of working can be identified before an outage forces those decisions. ### **Communication Runs Throughout the Response** Employees need reliable information about what is happening and what they should do. Depending on the incident, they may need to avoid certain applications, disconnect devices, use alternative systems, or change how they work temporarily. External communication requires its own coordination. Customers, business partners, insurers, regulators, or law enforcement may need to be contacted depending on the information and systems involved. Canadian privacy laws can also create [breach reporting and notification obligations](https://www.priv.gc.ca/en/report-a-concern/report-a-privacy-breach-at-your-organization/report-a-privacy-breach-at-your-business/?referral=79482820) in certain circumstances. Legal and privacy professionals can help determine which requirements apply and when notifications need to occur. Assigning responsibility for communication keeps information consistent as the situation changes. ### **Hours 12–24: Recovery Begins** By this point, responders may have a better idea of the incident scope, and which systems can safely begin returning to service. Recovery can include [restoring data,](https://yournucleus.ca/services/) resetting credentials, rebuilding devices, applying security updates, changing configurations, and validating systems before reconnecting them. Speed is important, but so is avoiding a repeat of the compromise. Systems need to be checked before they return to normal use, and monitoring may increase while responders watch for further suspicious activity. Serious incidents can take days or longer to resolve. The first 24 hours establish the direction of the response rather than marking the end of it. ### **What a Response Plan Changes** [A documented incident response plan](https://www.cyber.gc.ca/en/guidance/developing-your-incident-response-plan-itsap40003) gives the organization assigned roles, contact information, escalation procedures, communication responsibilities, and recovery priorities to work from. Without those decisions in place, the response team has to make them while also dealing with the incident. Plans need regular attention as the business changes. Contacts leave, systems are replaced, vendors change, and recovery priorities evolve. Reviewing and testing the plan keeps it aligned with the environment it’s designed to protect. ### **Be Ready Before the Clock Starts** Nobody knows exactly how a cyber incident will unfold, but businesses can prepare for the decisions they’re likely to face. Having clear guidance around who leads the response, who needs to be contacted, which operations take priority, and how employees receive instructions gives the organization a stronger starting point when time is limited. How would your first 24 hours look? [Nucleus can help you](https://yournucleus.ca/contact/) build an incident response process your team is ready to use. ### **FAQs: Responding to a Cyberattack** #### **What should a business do first after discovering a cyberattack?** Contact the people responsible for incident response and begin assessing what is known. Containment steps should reflect the type of incident and guidance from qualified IT or security responders. #### **Should you shut down systems during a cyberattack?** Not automatically. Shutting down systems can affect evidence, operations, or recovery. Decisions about disconnecting or powering down equipment should be guided by the circumstances and the incident response team. #### **Who should be contacted after a cyberattack?** Contacts may include IT and security teams, leadership, legal or privacy advisers, the organization's cyber insurer, incident response specialists, and relevant authorities. The appropriate contacts depend on the incident and applicable requirements. #### **How long does recovery from a cyberattack take?** Recovery time depends on the type and scope of the attack, affected systems, available backups, and the organization's preparation. Significant incidents can take days or longer to fully resolve. #### **What should an incident response plan include?** A plan should identify roles and responsibilities, escalation procedures, key contacts, communication processes, containment procedures, and recovery priorities. It should also be reviewed regularly as the organization changes. ![Nucleus Pulse Image](https://blog.yournucleus.ca/hubfs/nucleus-images/Group%20399.png) ![Picture of Karl Fulljames, CTO](https://blog.yournucleus.ca/hs-fs/hubfs/Karl-1.png?width=115&name=Karl-1.png) [Karl Fulljames, CTO](https://blog.yournucleus.ca/author/karl-fulljames-cto) ## We are local! WE HAVE PRESENCE IN VICTORIA, VANCOUVER, PRINCE GEORGE, CALGARY, AND TORONTO. 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