Exfiltration Over Webhook
Exfiltration Over Webhook [T1567.004]
Last updated
Exfiltration Over Webhook [T1567.004]
Last updated
Name: Exfiltration Over Webhook
ID: T1567.004
Tactics:
Technique:
Exfiltration Over Webhook (T1567.004) is a sub-technique within the MITRE ATT&CK framework under the Exfiltration tactic. This technique involves adversaries leveraging legitimate webhook services to covertly transfer stolen data out of compromised networks. Webhooks provide automated HTTP callbacks, typically used by legitimate applications to receive notifications or data updates. Attackers exploit these legitimate communication channels to blend malicious data exfiltration traffic into normal network activities, thus evading detection mechanisms.
Adversaries employing Exfiltration Over Webhook typically follow these technical methods and mechanisms:
Webhook Setup and Configuration:
Attackers first create or compromise webhooks on legitimate services (such as Slack, Discord, Microsoft Teams, GitHub, or other cloud-based providers).
They configure webhook endpoints to automatically accept and relay HTTP POST requests containing data payloads.
Data Preparation and Encoding:
Stolen data is often compressed, encrypted, or encoded (for example, Base64 encoding) to obfuscate the content and evade detection.
Attackers may segment large data sets into smaller chunks to avoid triggering data transfer thresholds or anomaly detection systems.
Execution of Data Transfer:
Adversaries use scripts or malware implants to send HTTP POST requests to the configured webhook endpoints.
These HTTP requests mimic legitimate application traffic, making detection challenging.
Attackers may use legitimate libraries or built-in scripting tools (such as PowerShell, Python scripts, or curl commands) to initiate the webhook requests.
Data Retrieval and Management:
After data transmission, attackers retrieve exfiltrated data from the webhook provider's platform or service.
They may automate the retrieval process to efficiently manage and analyze stolen information.
This sub-technique can appear at various stages of an attack lifecycle, including but not limited to:
Initial Access and Reconnaissance:
Attackers may test webhook exfiltration capabilities early in the attack to ensure data exfiltration channels are functional and undetected.
Credential Harvesting and Data Theft:
Adversaries frequently use webhook exfiltration after successfully stealing sensitive data, credentials, or intellectual property from compromised systems.
Command and Control (C2) Communications:
Webhooks can be leveraged as covert channels for command and control communications, allowing attackers to issue commands and receive responses covertly.
Persistence and Long-Term Operations:
Attackers may continuously leverage webhook exfiltration to maintain long-term, low-profile data exfiltration channels, ensuring persistent access to sensitive information.
Detection of Exfiltration Over Webhook can be challenging due to the legitimate nature of webhook traffic. However, several detection methods, tools, and indicators of compromise (IoCs) can help identify this technique:
Network Traffic Monitoring and Analysis:
Monitoring for unusual outbound HTTP POST requests to known webhook endpoints or cloud services.
Detecting sudden increases in webhook-related traffic or anomalous data volumes can indicate malicious use.
Endpoint Detection and Response (EDR) Tools:
EDR solutions can detect suspicious scripts or binaries initiating HTTP POST requests to webhook URLs.
Behavioral analysis and anomaly detection modules within EDR platforms can identify abnormal webhook usage patterns.
Web Proxy and Firewall Logs:
Reviewing proxy and firewall logs for unusual or unauthorized connections to webhook domains or known cloud services.
Identifying recurring or periodic webhook requests from internal hosts that are atypical for normal operations.
Security Information and Event Management (SIEM):
Correlating logs and alerts from multiple sources (endpoint logs, network logs, proxy logs) to identify suspicious webhook activity.
Creating custom SIEM rules to alert on webhook-related anomalies or suspicious traffic patterns.
Indicators of Compromise (IoCs):
Suspicious webhook URLs or domains appearing in network logs.
Unusual HTTP headers, payload structures, or encoded/encrypted data in webhook POST requests.
Anomalous outbound traffic to known webhook providers (Slack, Discord, Teams, GitHub, etc.).
Detecting Exfiltration Over Webhook is critical due to the following potential impacts and risks:
Data Breach and Information Leakage:
Attackers can exfiltrate sensitive data, intellectual property, and confidential information, causing severe damage to business operations, reputation, and regulatory compliance.
Detection Evasion and Stealth:
Webhook exfiltration leverages legitimate web services to evade traditional detection methods, allowing attackers prolonged and stealthy access to compromised networks.
Operational Security Risks:
Undetected webhook exfiltration can lead to attackers maintaining persistent footholds, enabling further exploitation, lateral movement, and long-term compromise.
Regulatory and Compliance Implications:
Undetected data exfiltration can result in non-compliance with data protection regulations (such as GDPR, HIPAA, PCI DSS), leading to legal penalties, fines, and reputational harm.
Early detection and response to webhook-based exfiltration attempts significantly reduce these risks, minimize data exposure, and mitigate potential damage to the organization.
Real-world examples of Exfiltration Over Webhook include:
Discord Webhook Abuse:
Threat actors have leveraged Discord webhooks to exfiltrate stolen credentials, browser history, and cryptocurrency wallet information.
Attackers embedded webhook URLs in malware payloads, which automatically POST stolen data to attacker-controlled Discord channels.
Slack Webhook Data Theft:
Attackers have used Slack webhooks to exfiltrate sensitive corporate data, including internal documents, customer information, and proprietary source code.
Malicious scripts were discovered that periodically POSTed encoded data to Slack webhook endpoints, blending in with legitimate Slack API traffic.
GitHub Webhook Exploitation:
Adversaries have utilized GitHub webhooks to exfiltrate source code and sensitive configuration files from compromised developer workstations.
Attackers configured malicious scripts that POSTed stolen data directly to GitHub repositories using webhook endpoints, making detection difficult due to legitimate GitHub traffic.
Microsoft Teams Webhook Misuse:
Attackers have exploited Teams webhooks to exfiltrate sensitive data such as emails, documents, and internal communications.
Malicious PowerShell scripts were utilized to POST encoded data to Teams webhook URLs, making the malicious traffic appear legitimate and difficult to detect.
In each scenario, attackers leveraged legitimate webhook services to evade detection, highlighting the importance of robust monitoring, detection, and response strategies to identify and mitigate Exfiltration Over Webhook threats.