Hacked? Here's What To Do: Incident Response Guide
Discovering your business has been hacked is stressful. Your mind races, your heart pounds, and you're not sure what to do first. Take a breath. This guide walks you through exactly what to do, step by step, to minimize damage and recover as quickly as possible.
Signs You've Been Hacked
The first step is recognizing that something is wrong. Here are common signs of a security breach:
Unusual system behavior
Slow performance, crashes, programs starting on their own
Locked out of accounts
Passwords no longer work, unexpected password reset emails
Ransom messages
Files encrypted, messages demanding payment
Strange network activity
Unexpected data transfers, connections to unknown servers
Security alerts
Warnings from antivirus, firewall, or monitoring tools
Customer complaints
Reports of spam from your email, suspicious invoices
Immediate Steps: The First 15 Minutes
When you suspect a breach, these first actions are critical:
Don't panic
Take a breath. Rushed decisions often cause more damage. You have time to think.
Document what you see
Take photos of screens, note error messages, timestamps. This evidence is crucial.
Don't turn off computers
Unless ransomware is actively spreading. Evidence may be lost on shutdown.
Isolate affected systems
Disconnect from network (unplug cables, disable Wi-Fi). Don't turn off.
Call your IT partner
If you have one, contact them immediately. They can guide next steps.
Step-by-Step Response Plan
Contain
Stop the spread
- Disconnect affected computers from the network
- Disable remote access and VPN connections
- Change passwords for critical accounts (from a clean device)
- Block suspicious IP addresses at the firewall
- Preserve evidence—don't delete or modify anything
Assess
Understand what happened
- Identify which systems are affected
- Determine what data may be compromised
- Check backup systems—are they intact?
- Review security logs for entry point
- Identify the type of attack (ransomware, data theft, etc.)
Communicate
Inform the right people
- Brief management and key staff
- Prepare customer communication if data affected
- Notify cyber insurance provider
- Consider legal counsel for GDPR obligations
- Document all communications
Recover
Restore operations
- Verify backups are clean before restoring
- Rebuild systems from known-good images
- Restore data from offline backups
- Reset all passwords across the organization
- Patch vulnerabilities that enabled the attack
Report
Notify authorities if required
- NIS2: Report significant incidents within 24 hours
- GDPR: Notify data protection authority within 72 hours if personal data affected
- File police report for criminal investigation
- Notify CCB at cert@ccb.belgium.be for technical assistance
Learn
Prevent it from happening again
- Conduct post-incident review
- Identify what allowed the attack to succeed
- Update security policies and procedures
- Implement additional security controls
- Train staff on lessons learned
Who to Contact
Having the right contacts ready before an incident saves precious time:
NIS2 Reporting Requirements
If your organization falls under NIS2, you have strict reporting obligations:
Should You Pay the Ransom?
This is one of the most difficult decisions businesses face. Our recommendation: don't pay.
Why not to pay:
- No guarantee you'll get your data back
- Funds criminal organizations and encourages more attacks
- Paying marks you as a target for future attacks
- Decryption tools often don't work properly
- May violate sanctions regulations
Cyber Insurance Considerations
If you have cyber insurance, act quickly:
- Notify your insurer as soon as possible (check policy for timeframe)
- Document everything—insurers need evidence for claims
- Follow their incident response requirements
- Keep receipts for all incident-related expenses
- Don't admit liability without consulting your insurer
Preventing the Next Attack
Once you've recovered, strengthen your defenses:
Frequently Asked Questions
How do I know if I've been hacked?
Common signs include: unusual system slowness or crashes, locked accounts, ransom messages, unexpected password resets, strange emails sent from your accounts, or alerts from security software. If something feels wrong, investigate. Trust your instincts.
Should I turn off my computer?
Usually no. Turning off a computer can destroy forensic evidence in memory. Instead, disconnect it from the network (unplug the ethernet cable, disable Wi-Fi) but leave it running. The exception: if ransomware is actively encrypting files and spreading, shutting down may limit the damage.
Do I need to report a breach?
It depends. Under GDPR, breaches involving personal data must be reported to the data protection authority within 72 hours if they pose a risk to individuals. Under NIS2, significant incidents must be reported within 24 hours. Even if not legally required, reporting to CCB (cert@ccb.belgium.be) can help you get assistance and helps protect others.
Should I pay a ransom?
We strongly advise against it. There's no guarantee you'll get your data back, it funds criminal organizations, and it marks you as a target for future attacks. Focus on restoring from backups instead. If you don't have backups, consult with law enforcement and cybersecurity experts before making any decisions.
How can I prevent this from happening again?
Focus on the basics: maintain regular tested backups (with offline copies), enable multi-factor authentication everywhere, keep systems patched and updated, train employees to recognize phishing, and have an incident response plan ready. Consider implementing the CyberFundamentals framework for structured security improvement.
Related Articles
Sources
- CCB CERT Belgium — Computer Emergency Response Team
- NIS2 Directive (EU) 2022/2555 — Incident reporting requirements
- IBM Cost of a Data Breach Report — Breach statistics and costs
- ENISA — EU Agency for Cybersecurity