Clone phishing, also known as a “cloning attack,” is a targeted email-based deception. It reuses legitimate messages or design elements to trick recipients. The aim is to make them reveal login details, install malware, or do harmful actions. This post explains the attack techniques and differences from related scams. It covers technical signs and real-world patterns. You will learn about detection strategies and prevention best practices. It also includes incident response steps and a practical checklist you can apply right away.

What is clone phishing?

Definition: Clone phishing is an email attack. An attacker takes a legitimate email, often one earlier sent by a trusted sender or vendor. They duplicate (or “clone”) its content, layout, and attachments/links. The attacker then replaces one or more safe links or attachments with malicious links or payloads. Because the cloned message mirrors a known legitimate email, recipients are more to trust and interact with it.

Key characteristics:

• Uses a legitimate email as a template.
• Preserves branding, wording, and formatting.
• Changes a link or attachment to lead to an attacker-controlled resource.
• Often sent from a location that appears to be legitimate (or from a compromised account).

Clone phishing vs. related attacks

• Spoofing: Spoofing is forging sender details (From: header, show name). Clone phishing often uses spoofing, but the defining trait of cloning is reusing a legitimate message’s content.
• Spear-phishing: Targeted phishing against specific individuals or organizations. Clone phishing can become spear-phishing when an attacker targets a specific person. They use a cloned email relevant to the targeted person.
• Business Email Compromise (BEC): BEC involves social-engineering to trick people into transferring money or sensitive data, often leveraging compromised accounts. A clone-phish is used to spread malware as part of a BEC campaign.
• Whaling: High-value target phishing (executives). Clone-phishing is used for whaling if the cloned message is tailored for an executive.

Anatomy of a clone-phishing attack

1. Reconnaissance
   • Attacker obtains a copy of a legitimate email. Sources: intercepted emails, public mailing lists, leaked mailboxes, or a prior successful phishing.
2. Preparation
   • Duplicate the exact content and layout.
   • Replace safe link(s)/attachment(s) with malicious equivalents (credential harvesters, remote payload hosts, trojanized documents).
   • Adjust metadata to increase legitimacy (reply-to, topic, thread references).
3. Delivery
   • Send the cloned message to targets. Delivery vectors:
     • From attacker-controlled domain like original.
     • From compromised legitimate account (most convincing).
     • Using show-name spoofing plus small sender-location modifications.
4. Exploitation
   • Victim clicks link or opens attachment.
   • Outcomes: credential theft, malware infection, lateral access, data exfiltration.
5. Post-exploitation
   • Use harvested qualifications to pivot, send further clones internally, or escalate to follow-on fraud.

Common goals and payloads

• Credential harvesting: fake sign-in pages that capture usernames and passwords.
• Malware delivery: RCE trojans, Remote Access Trojans (RATs), ransomware via malicious documents or executables.
• Account compromise: attackers use malicious links to obtain session tokens. They also acquire 2FA bypass codes. Attackers trick victims into approving OAuth consents.
• Fraud/financial theft: get employees to transfer funds or reveal payment details using a cloned vendor invoice email.
• Lateral propagation: compromise one account to send clone emails internally (increases believability).

Real-world patterns and example scenarios

(These are composite, realistic scenarios anonymized and generalized.)

• Vendor invoice clone: Finance receives a cloned invoice email from a trusted vendor. The email has an attachment that, when opened, runs a macro. This macro installs ransomware.
• File-sharing update clone: An employee receives a “shared document” update. It seems to come from an internal collaboration tool. But, the link leads to a credential-phishing page. This page is hosted on a domain that visually mirrors the real service.
• Internal HR memo clone: Attackers harvest an old HR email about benefits. They send a cloned “update” requiring login. This credential capture leads to internal data access.
• Password-reset clone: A cloned password reset email points to a page that asks for old and new passwords. The attacker collects both passwords. Then, they log into real systems.

Technical indicators and how to spot them

Headers and metadata

• Mismatch between show name and the actual sender location.
• Return-Path or Received headers originating from unfamiliar IPs or countries.
• DKIM or SPF failures legitimate domains usually pass both; cloned emails not.

URLs and links

• URLs that use deceptive domains (extra hyphens, subdomain tricks like login.example.com.attacker.com).
• Shortened links with no preview or links that redirect multiple times.
• HTTPS padlock alone is not proof of legitimacy attackers can obtain certificates.

Attachments

• Macro-enabled Office documents (.doc, .xls) with prompt to “Enable Content”.
• Executable attachments or archives (.exe, .zip, .scr) disguised as safe files.
• Mismatched content-type and file extension.

Message content

• Slight grammar/formatting inconsistencies vs. the original legitimate email.
• Changed call-to-action (e.g., “view updated invoice” where original said “invoice attached”).
• Unusual urgency, threats, or instructions contradicting normal processes.

Behavioral

• Unexpected email in an existing thread cloned message can share topic but ask to carry out different action.
• Recipient receives the message even though original sender doesn’t typically send to that person.

Defenses: prevention, detection and user training

Technical controls (in order of priority)

1. Email authentication
   • Enforce and monitor SPF, DKIM, and DMARC with a reject/quarantine policy for failing mail.
2. Blocklist/allowlist controls
   • Block risky file types at gateway; allowlist known-safe senders and domains when appropriate.
3. Safe browsing and URL rewriting
   • Email security gateways that rewrite and inspect links in real-time; sandbox link clicks.
4. Attachment sandboxing
   • Detonate attachments in a sandbox to detect malicious behavior before delivery.
5. Multi-factor authentication (MFA)
   • Enforce strong MFA prefer phishing-resistant techniques (hardware keys, FIDO2) where possible.
6. Least privilege and segmentation
   • Limit the scope of what a compromised account can access; use network segmentation.
7. Endpoint protection
   • EDR that detects malicious macros, suspicious process chains, abnormal persistence, and credential dumping.
8. Data loss prevention (DLP)
   • Watch for sensitive data exfiltration which can follow a successful compromise.
9. Logging and SIEM
   • Centralize logs and set alerts for anomalous logins, mailbox rules creation, or mass email sending.

Process and policy

• Vendor verification procedures: Need multi-step verification for payment changes or invoice updates (e.g., confirm over phone on a known number).
• Emailing sensitive actions: Never accept login details over email or follow payment/invoice instruction without secondary verification.
• Account lifecycle policies: Periodic reviews of external sharing and delegated mailbox access.

User education (must be ongoing)

• Teach employees to:
  • Inspect links via hover before clicking.
  • Confirm unexpected requests via separate channels (phone, in-person).
  • Be suspicious of “thread hijacks” where a reply says something different from the original.
• Phishing simulations: run regular, realistic simulations that include cloned-email styles.
• Teach how to report suspicious mail quickly and easily (one-click reporting to security team).

Incident response and containment

Immediate actions (first 60–90 minutes):

1. Find and isolate affected accounts and endpoints.
   • Disable compromised accounts or force immediate password change plus revocation of active sessions.
   • Isolate infected endpoints from the network if malware is detected.
2. Preserve evidence
   • Snapshot mail headers, the phishing message, and affected endpoints’ memory/disk images as needed.
3. Block infrastructure
   • Take down or block attacker domains/IPs at the firewall and email gateway.
4. Rotate login details and tokens
   • Revoke API keys, OAuth grants, and reset access details for affected services.

Follow-up actions (hours–days):

• Forensic investigation: find first access vector, extent of compromise, and data accessed.
• Remediation: remove persistence, clean or rebuild compromised endpoints.
• Notification: inform stakeholders and, if required, regulatory bodies and customers per policy.
• Post-incident: lessons learned, update prevention controls, and run targeted training.

Tools and technologies that help

• Email security gateways (for SPF/DKIM/DMARC enforcement, link rewriting, attachment sandboxing).
• Secure Web Gateways (SWG) for runtime link inspection and blocking of malicious sites.
• Endpoint Detection and Response (EDR) to detect payload execution and lateral movement.
• SIEM / SOAR for alerting and automated containment playbooks.
• Phishing simulation platforms for ongoing awareness training.
• Password managers and MFA hardware tokens to reduce credential re-use risk and phishing success.
• DNS monitoring / RPZ to block known malicious domains quickly.

Quick checklist actionable items

For IT/security teams

• Publish and enforce DMARC policy set to quarantine or reject.
• Allow link rewriting and attachment sandboxing at the email gateway.
• Enforce MFA for all remote and privileged accounts; rank phishing-resistant MFA.
• Set up EDR and set escalation alerts for suspicious email-driven behavior.
• Implement a formal vendor confirmation process for payment/invoice changes.
• Run regular phishing simulations that include cloned-email templates.
• Keep an incident playbook for email-based attacks.

For end users

• Hover over links don’t rely on visible text alone.
• Don’t allow macros in Office documents unless they are verified and expected.
• Verify requests for payments or sensitive info by calling a known number, not numbers supplied in the suspicious email.
• Use password managers to avoid manual credential entry on fake sites.
• Report suspicious emails using the company’s reporting button.

Closing / key takeaways

• Clone phishing is highly effective because it leverages the trust in an existing, legitimate message.
• Preventive controls (SPF/DKIM/DMARC, sandboxing, link rewriting) merged with phishing-resistant MFA and endpoint protection dramatically reduce risk.
• Quick incident response, robust logging, and user reporting accelerate containment and limit impact.
• Humans stay critical: continuous training and simple reporting processes significantly decrease the success rate of cloning attacks.