An effective incident response plan is critical for cybersecurity teams facing active threats.
When a cyberattack happens, a quick response is imperative. The longer attackers remain within a perimeter, the more they can accomplish, from transferring data to disrupting services and compromising credentials.
Preparation is key, even for security professionals with access to a one-click response solution. Being ready means relying on ingenuity and know-how to think on one’s feet, using creative workarounds to stop attackers in their tracks. But it also demands careful planning.
Network segmentation needs to be fastidiously applied, the appropriate admin privileges must be ready through just-in-time access, and a documented asset inventory and tiered user account strategy are required to minimize potential disruption.
In this article, we’ll walk through the steps needed for a robust cybersecurity incident response plan.
Develop and rehearse your incident response plan
Don’t just plan it, test it: Peacetime lockdown drills are an essential exercise for having a strong incident response playbook.
Incident response plans give your security team a standardized process to learn, rehearse, and structure their responses around. Remediation actions will be coordinated and applied quickly and strictly when team members know clearly who is responsible for what ahead of time.
Playbooks also give incident triage and documentation a reliable format and outline communication protocols and responsibilities across appropriate teams and third parties. Incident analysis and retrospective actions are improved, leaving teams better prepared to proactively discover and triage incidents in the future.
Hold tabletop exercises that simulate real-life attacks to give your team a chance to execute their playbook and put their readiness to the test.
Step 1: Identify threat and scope
Every step toward resolving an attack depends on first determining its scale and form. Is this a single infected endpoint, a compromised account, or a wider breach? Look for key indicators, such as unusual network traffic, spikes in CPU usage, failed or unauthorized login attempts, or suspicious activity in tools like PowerShell.
Performing digital triage means seeking out the symptoms. Check event management, endpoint detection and response (EDR), and firewall logs for anything out of the ordinary, and inspect DNS and proxy logs to identify suspicious outbound requests.
Jump to conclusions, but back up your hypotheses with endpoint telemetry to avoid wasting time on false positives.
At the same time, it’s essential to collect forensic data that will facilitate later root-cause analysis and subsequent remedial action. Pull memory dumps of active processes and records of network activity.
Event logs, such as Windows Event Viewer, Sysmon, or cloud logs, can paint a clear picture of what’s happening.
Step 2: Isolate compromised systems and endpoints
Lateral movement is dangerous. The further attackers can reach, the more chaos they can cause. As soon as a system is identified as compromised, it must be cut off from any potential connecting nodes.
This means blocking switch ports or using firewall rules to stop all inbound and outbound traffic, quarantining affected endpoints in a restricted VLAN, and immediately revoking connections, such as VPNs or Wi-Fi access.
Block traffic at the network level by applying deny rules to firewalls from known malicious IPs and domains. Block suspicious domains at the DNS level when possible. And monitor network flows for command-and-control connections; savvy attackers often hide in unexpected places.
Step 3: Harden all systems against further exploitation
It’s wise to limit attack surface and temporarily disable unnecessary features, such as file shares, SMB and RDP access, and PowerShell remoting. Although, realistically, it is best to put these precautions in place before an attack happens, building them into a robust security policy.
Facing an attack, administrators should also consider applying quick-fix hardening actions. If a clear vulnerability has been discovered, it should be patched as a matter of urgency. Privileged accounts should receive stricter multi-factor authentication (MFA) policies to reduce the risk of a secondary compromise.
Application Allowlisting must be enabled, and the running of unsigned scripts must be disabled wherever possible. Raise the bar for attackers, and you lower the risk of further damage.
Step 4: Contain compromised accounts and credentials
If attackers have gained control of legitimate credentials—whether from leaked information, authentication misconfigurations, or malicious insiders—it is essential to cut off their access.
Resetting the passwords of all affected or suspected accounts and forcing a global sign-out is a good starting point, as it also disables potentially compromised Active Directory or cloud accounts.
An account possesses more than its direct credentials, of course. In cloud environments, API keys and session tokens should be immediately revoked to disrupt active attacks.
Step 5: Maintain clear communication
While many sectors have regulatory reasons to disclose attacks to third parties and stakeholders quickly, internal communication takes priority in the early stages.
Clearly assign someone to coordinate response efforts. Alert leadership and key teams without over-communicating to all staff. Use secure, out-of-band communication platforms, like a dedicated email platform distinct from your business domain, to effectively protect and obscure remediation efforts from the eyes of attackers.
Talk, work together, and form a united front.
A Zero Trust approach to cybersecurity incident response
Preparation is key. Practicing attacks, pen-testing systems, and clearly documenting and firmly enshrining defensive procedures before an attack happens ensures that any reactive efforts are as strong as they can be.
However, prevention should be the first step with any incident response plan.
With Zero Trust architecture in place, anything not previously verified and approved is denied. Whether it’s applications, users, specific actions, or scripts, if your team hasn’t approved it, it’s blocked.
This includes having strong policies and Zero Trust capabilities in place to support your incident response playbook.
ThreatLocker Allowlisting prevents any unknown software from executing meaning rogue installs, unsanctioned tools, and hidden software are all blocked by default.
Ringfencing™ enforces strict boundaries on what applications can access various tools and resources, limiting lateral movement and blocking fileless or toll-chaining attacks.
EDR real-time threat detection acts instantly when it detects abnormal activity by automatically blocking excessive writes, isolating affected machines, and shutting down risky tools.
There will always be a need for security readiness, just as there will always be the possibility of an attacker attempting a breach. But there are different levels of preparedness, and the more comprehensive your incident response plan, the less likely an active attack will turn into a long-term problem.
