What To Do After a Phishing Attack: A Practical Incident Response Guide for Businesses
Author :
Deepak Saini
Dec 9, 2025
Phishing attacks are no longer isolated events — they are a persistent operational threat. Nearly every modern cyber breach starts with a human falling for a deceptive email, fake website, or fraudulent message. While organizations invest millions in tools, one emotional click can still bypass defenses.
But here’s the critical truth: a phishing incident doesn’t have to become a breach disaster if the response is fast, smart, and structured.
In this guide, we break down exactly what to do after a phishing attack — based on real-world incidents and professional incident response methodologies. Whether you are an IT leader, SOC analyst, or a business owner managing risk, these actions will help you limit damage and recover quickly.
Don’t Panic. Immediately Isolate the Threat
The first moments after detection matter most.
When an employee reports or realizes they clicked a malicious link or shared information, treat it as a confirmed incident — not a hypothetical one.
Take these immediate actions:
Disconnect the infected device from the corporate network (Wi-Fi, VPN, LAN)
Do not shut down the machine — volatile forensic data could be lost
Revoke or reset compromised credentials immediately
If malware is suspected, contain — don’t delete the malicious file for forensic analysis
Real-world example:
In 2023, a manufacturing company avoided a full ransomware attack after a phishing email executed a malicious loader. The user unplugged their device instantly and called IT. Analysts contained the threat before lateral movement — a decision that saved millions.
Rule of thumb:
The faster the containment, the smaller the blast radius.
Assess the Impact: Identify What Data or Access Was Compromised
Phishing attacks aren’t always about stealing passwords — they may aim to:
- Deploy malware
- Intercept payment details
- Gain privileged access
- Initiate fraudulent transactions
A thorough impact assessment should answer:
Was any sensitive data shared (passwords, personal data, financial info)?
Was Multi-Factor Authentication (MFA) enabled on the account?
Did the attack originate from a known threat actor group or domain?
Were any files downloaded, or processes executed?
Cybersecurity teams should:
Analyze email logs and browser history
Review endpoint telemetry (EDR alerts, suspicious processes)
Check for lateral movement and privilege escalation attempts
If financial data or PII was exposed, escalate severity classification immediately.
Eradicate the Threat and Remove Persistence
Once the scope is known — eliminate all malicious artifacts.
This may include:
Removing malware payloads
Blocking malicious IPs, domains, and sender addresses
Revoking session tokens and API keys
Reviewing OAuth third-party access (common in Microsoft 365 phishing)
Checking for backdoors (registry modifications, scheduled tasks)
If ransomware or credential-stealer malware was detected, you may need a complete OS rebuild to fully ensure integrity.
Reset and Harden Affected Accounts
Password resets alone are often not enough.
Apply layered security enhancements:
Enforce strong MFA (preferably phishing-resistant FIDO2 / WebAuthn keys)
Update endpoint security software
Review access privileges — remove any unnecessary admin rights
Apply conditional access rules to restrict risky login attempts
If email accounts are compromised, attackers may create:
Inbox forwarding rules — used for silent data exfiltration
Fake mail filters — hiding threat-actor communications
Impersonation messages — continuing the attack internally
Audit these thoroughly.
Report the Incident Internally and Externally
Transparency prevents further internal spread — silence amplifies damage.
Notify:
Cybersecurity / Incident Response team
Leadership and Legal team
Data Protection Officer (for compliance)
Affected stakeholders (employees, partners, customers)
When required by law:
Report to regulatory bodies like CERT-In, GDPR authorities, etc.
Notify banks if financial fraud is involved
If payment redirection occurred (Business Email Compromise):
Immediately inform the bank’s fraud response team
File a cybercrime report with local authorities
Time is critical — fast reporting increases the chance of fund recovery.
Communicate With Your Team — Turn the Incident Into a Teachable Moment
Phishing attacks thrive on silence and shame.
Instead:
Share what happened
Explain the technique the attacker used
Highlight early detection success stories
Embed lessons into ongoing awareness training:
Recognizing emotional manipulation (urgency, fear, authority)
Hovering over links before clicking
Reporting suspicious activity without hesitation
Cybersecurity culture is built through trust, not blame.
Conduct a Post-Incident Review (PIR) and Update Defenses
Every incident is valuable intelligence.
Perform a full PIR including:
Attack vector analysis: how did phishing bypass controls?
MITRE ATT&CK mapping: which techniques were used?
Security gaps: missing DMARC, weak MFA, poor segmentation?
Human behavior triggers: why did the user engage?
Then strengthen the human and technical controls:
Advanced phishing simulations with real-life pretexts
Psychological-driven vulnerability analytics
Enhanced email filtering with DMARC, SPF, DKIM enforcement
Secure email gateways and sandbox isolation
Identity threat detection & response (ITDR)
A phishing attempt that gets through is not a failure —
a phishing repeat is.
Real-World Cases: What We Can Learn
Incident | Attack Type | Impact | Key Lesson |
|---|---|---|---|
CFO impersonation email led to fraudulent wire transfer | Business Email Compromise | $2.5M loss | Approvals for large transactions must require out-of-band verification |
Fake Microsoft login page captured Office 365 credentials | Account Takeover | Data access + internal phishing chain | MFA + continuous monitoring could have blocked takeover |
HR-targeted fake resume PDF delivered remote access trojan (RAT) | Malware Deployment | Potential ransomware spread | Network segmentation and EDR containment stop escalation |
Credential leak through fake VPN login portal | Privilege Escalation | Domain admin compromise attempt | PAM + password vaulting reduces credential abuse |
Each organization that recovered successfully did ONE thing right:
They treated human error as an intelligence signal, not negligence.
Invest in Proactive Human-Centric Defense
Technology does not fail — humans are targeted.
Modern attackers exploit emotions:
Fear → “Your account will be locked”
Curiosity → “Urgent invoice attached”
Authority → “Payment request from the CEO”
Greed → “Tax refund approval”
Empathy → “Help a sick colleague”
At ClearPhish, we’ve seen the highest-risk employees aren’t careless — they’re emotionally vulnerable at the wrong moments.
That’s why hyper-realistic phishing simulations, story-based awareness, and Emotional Vulnerability Index scoring are now becoming essential to cyber defense.
Conclusion: A Phishing Attack Is Not the End — It’s a Beginning
Every organization will face phishing. Not every organization must become a victim of it.
If you act quickly:
✔ Contain the threat
✔ Secure accounts
✔ Investigate thoroughly
✔ Educate continuously
You convert an incident into resilience. The ultimate goal is not to prevent every emotional click — but to ensure one click doesn’t take down your entire business.
