In today’s evolving threat landscape, security incidents
are inevitable. How you respond to them determines the extent of damage and
your organization’s resilience. Whether you’re dealing with a phishing attack,
malware, a data breach, or a misconfiguration, a well-defined incident
response process is crucial.
In this post, we’ll walk through a practical, structured
approach to handling security incidents, based on best practices from the NIST
Cybersecurity Framework and ISO/IEC 27035.
What is a Security Incident?
NIST SP 800-61 Rev. 2 defines an incident as:
"A violation or imminent threat of violation of
computer security policies, acceptable use policies, or standard security
practices."
A security incident is any event or series of events
that indicate a potential breach or violation of an organization’s information
security policies, acceptable use policies, or standard security practices. It
often involves unauthorized access, use, disclosure, modification, or
destruction of information or systems, and may impact confidentiality,
integrity, or availability (CIA triad).
The Three Pillars:
- Confidentiality:
Preventing unauthorized disclosure of information, like using encryption
or access controls to keep sensitive data secret.
- Integrity:
Maintaining the accuracy, consistency, and trustworthiness of data,
protecting it from unauthorized changes or destruction (e.g., backups,
checksums).
- Availability:
Ensuring authorized users can reliably access information and systems when
needed, through measures like redundancy, disaster recovery, and DoS
protection.
Key Characteristics of a Security Incident:
- Unauthorized
Activity
An attempt to access or modify data or systems without authorization. - Policy
Violation
Activity that goes against internal security controls or procedures. - Threat
Indicators
Evidence of malware, phishing, data exfiltration, or insider misuse. - Potential
Harm
May result in data loss, service disruption, regulatory fines, or reputational damage.
Common Types of Security Incidents:
- Phishing
attacks – where attackers trick users into giving up credentials or
downloading malware.
- Malware
infections – including ransomware or trojans on endpoints or servers.
- Data
breaches – unauthorized access and/or theft of sensitive data.
- Insider
threats – malicious or negligent actions by employees or contractors.
- Denial-of-Service
(DoS/DDoS) attacks – aimed at making a system or service unavailable.
- Cloud
misconfigurations – such as publicly exposed storage buckets or
permissive IAM roles.
Incident Response: Cloud Provider Security Response Teams
(Azure, AWS, GCP)
When operating in Azure, AWS, or GCP,
your cloud provider has dedicated internal security teams that can assist
during high-severity security incidents, such as:
- Suspected breaches of cloud infrastructure
- Data exfiltration concerns
- Compromised credentials with cloud-wide impact
- Abuse or misuse of cloud services
- Suspected platform-level vulnerabilities or service
compromise
The Microsoft Security Response Center (MSRC) is responsible
for investigating and responding to security incidents affecting Microsoft
services and infrastructure.
AWS Security is responsible for responding to issues
affecting AWS’s own infrastructure or abuse of their services. For incidents in
your own environment, you are the primary responder, but AWS can assist in platform-level
issues or abuse cases.
Google Cloud’s Cybersecurity Action Team (GCAT) provides
strategic and technical incident support to enterprise customers. Google also
has Security Command Center (SCC) and Chronicle for threat detection.
Step 1: Preparation
Before an incident even occurs, preparation is essential.
Without it, your team will be reactive and either slow or don’t know how to
respond.
Key Activities:
- Develop
an Incident Response Plan (IRP) that outlines roles, responsibilities,
communication protocols, and escalation procedures.
- Train
your team on common attack vectors and run regular simulations or tabletop
exercises.
- Implement
monitoring tools:
- Security
Information and Event Management (SIEM) tools like Splunk, Microsoft
Sentinel, Cortex XSIAM is SIEM+XDR+SOAR, QRadar.
- Endpoint
Detection and Response (EDR) platforms like CrowdStrike, Cortex XDR, Microsoft
Defender for Endpoint, Prisma, Threat Locker
- Network
monitoring tools like Zeek or Suricata
- Ensure
all systems are logging security-relevant events and that logs are stored
securely and centrally.
Preparation includes securing cloud resources as well. Tools
like AWS GuardDuty, Azure Security Center, and Google Cloud’s Security Command
Center can provide native visibility into cloud workloads.
Step 2: Detection and Analysis
Once a potential incident is suspected, the next step is detecting
and verifying the event.
How to Detect an Incident:
- Monitor
alerts from:
- SIEM dashboards
- Email security gateways
- Cloud security platforms
- IDS/IPS systems like Perimeter Firewalls
- Encourage
users to report suspicious behavior such as phishing emails or system
slowdowns.
How to Analyze the Incident:
- Identify
affected systems and users.
- Correlate
logs to determine the source and scope of the incident.
- Check
for Indicators of Compromise (IOCs), such as:
- Unusual login times or locations
- Unexpected network traffic
- File integrity changes
- Unknown processes or binaries
Tools to Use:
- Use SIEM to create timelines and identify patterns.
- Use endpoint tools to capture forensic data
(processes, registry changes, file hashes).
|
Forensic Tool |
Type |
Key Use Case |
|
Velociraptor |
Open-source |
Enterprise live forensics |
|
KAPE |
Free |
Fast artifact collection |
|
FTK Imager |
Free |
Full disk/image acquisition |
|
Magnet RAM Capture |
Free |
RAM dump |
|
Redline |
Free |
In-depth memory/process analysis |
|
GRR |
Open-source |
Scalable remote collection |
|
Sysinternals |
Free |
Manual triage |
|
Cortex XDR |
Commercial |
Integrated Palo Alto forensic
collection |
|
CrowdStrike RTR |
Commercial |
Remote forensics with scripting |
- For web or API attacks, analyze WAF logs and
application logs.
- In cloud environments, examine audit trails such as
AWS CloudTrail, Azure Activity Logs, or GCP Audit Logs.
Example:
If you receive an alert for suspicious login from a foreign country, verify it
against sign-in logs and determine whether MFA was bypassed.
Step 3: Containment
After confirming the incident, immediately take steps to contain
the damage and stop the attack from spreading.
Short-Term Containment:
- Isolate and/or Disconnect affected machines from the
network.
- Revoke access tokens or API keys.
- Disable compromised accounts or Force change
passwords.
- Block malicious IPs or domains in firewalls or cloud
security groups.
Long-Term Containment:
- Patch any vulnerabilities that were exploited.
- Update firewall rules or WAF policies to prevent
further exploitation.
- Segregate sensitive data and services from the rest
of the network.
Cloud:
If a compromised IAM user in Azure/AWS is discovered:
- Disable or delete their access keys.
- Attach a deny-all policy to the user or role.
- Rotate credentials immediately.
Step 4: Eradication
Once contained, the next goal is to eliminate the root cause
and ensure the threat is removed.
Key Steps:
- Remove malware or malicious code.
- Delete backdoors or persistence mechanisms.
- Clean registry or service entries added by attackers.
- Restore altered files from clean backups.
- Identify and patch vulnerable applications or
services.
Tools and Techniques:
- Use antivirus or EDR solutions to scan and remove
malicious payloads.
- Review and clean crontabs, startup scripts, scheduled
tasks, or registry keys.
- In the cloud, check for modified security groups, IAM
roles, or resource policies.
Always validate that eradication was successful. Perform a
full scan and re-check logs for lingering activity.
Step 5: Recovery
After the environment is clean, begin restoring systems to
operational status.
Best Practices:
- Rebuild compromised systems from clean images.
- Restore data from backups and verify integrity.
- Monitor systems closely after bringing them back
online.
- Re-enable access with secure credentials and enforce
MFA.
Cloud Recovery:
In AWS or Azure, use infrastructure-as-code (Terraform, CloudFormation, ARM
templates) to redeploy services consistently and securely.
Keep impacted users or customers informed, especially if there are regulatory
obligations under GDPR, HIPAA, or other data protection laws.
Step 6: Post-Incident Activity
After recovery, take time to learn from the incident and
improve defenses.
Activities to Perform:
- Conduct a Root Cause Analysis (RCA) to
determine how the incident happened and what can prevent it next time.
- Review what worked and what didn’t in your IR
process.
- Update documentation and playbooks.
- Share IOCs with threat intelligence platforms or
industry partners.
- Conduct a debriefing with all stakeholders.
Example of Lessons Learned:
- The
phishing email bypassed security filters - update email rules and user
training.
- MFA
wasn’t enforced – mandate MFA for all accounts.
- A
known vulnerability wasn’t patched – improve vulnerability management
program.
Final Thoughts
Security incidents will happen, but their impact can be
greatly reduced with the right processes, tools, and discipline. By following a
structured approach like the one outlined above, you can protect your
organization, maintain trust, and continuously improve your security posture.
Stay proactive. Stay prepared. Incident response is not just
a technical task it's a business-critical capability.
