Exfiltration Over Symmetric Encrypted Non-C2 Protocol

Exfiltration Over Symmetric Encrypted Non-C2 Protocol [T1048.001]

Information

• Name: Exfiltration Over Symmetric Encrypted Non-C2 Protocol

• ID: T1048.001

• Tactics: TA0010

• Technique: T1048

Introduction

Exfiltration Over Symmetric Encrypted Non-C2 Protocol (T1048.001) is a sub-technique under the MITRE ATT&CK framework's "Exfiltration Over Alternative Protocol" category. This technique involves adversaries exfiltrating sensitive data from compromised systems or networks using symmetric encryption methods over protocols not typically associated with Command and Control (C2) communications. The primary goal is to evade detection by disguising data exfiltration as legitimate encrypted traffic, making it challenging for defenders to differentiate malicious activities from normal traffic.

Deep Dive Into Technique

Adversaries employing this sub-technique typically leverage symmetric encryption methods to encode stolen data prior to exfiltration. Symmetric encryption uses the same cryptographic key for both encryption and decryption, making it efficient and suitable for large volumes of data. Common symmetric encryption algorithms used include AES (Advanced Encryption Standard), DES (Data Encryption Standard), and Blowfish.

Technical execution methods and mechanisms:

• Encryption of Data:

  • Attackers first gather sensitive information from compromised hosts or databases.

  • They utilize symmetric encryption algorithms (AES, DES, Blowfish) to encrypt the data, significantly reducing the risk of detection by data loss prevention (DLP) solutions that rely on plaintext pattern matching.

• Use of Non-C2 Protocols:

  • Adversaries avoid traditional Command and Control channels and instead leverage protocols typically seen as benign or legitimate, such as DNS, HTTP(S), FTP, SMTP, cloud storage APIs, or messaging services.

  • Encrypted data is encapsulated within legitimate protocol traffic, making it difficult for defenders to distinguish malicious communication from normal business operations.

• Data Transfer and Exfiltration:

  • Attackers may fragment encrypted data into smaller segments to further evade detection.

  • Data fragments may be transmitted slowly over time (low and slow approach), blending into routine network traffic patterns.

Real-world procedures:

• Attackers may use custom-developed malware or publicly available tools such as OpenSSL, GPG, or custom scripts to encrypt data.

• They often leverage legitimate cloud storage services (e.g., Dropbox, Google Drive, AWS S3), email services, or DNS tunneling to exfiltrate encrypted data.

• Attackers may employ obfuscation techniques like Base64 encoding or steganography in combination with symmetric encryption to further complicate detection.

When this Technique is Usually Used

This sub-technique can appear at various stages of an attack lifecycle, primarily during the exfiltration phase, after attackers have successfully gained access to sensitive data. Common scenarios and stages include:

• Post-Exploitation Phase:

  • After initial compromise and lateral movement, attackers encrypt sensitive data before exfiltration to avoid triggering alarms from security tools.

  • Commonly used after reconnaissance and data collection phases to securely move data out of the victim network.

• Advanced Persistent Threat (APT) Campaigns:

  • APT groups frequently utilize this technique due to its stealthy nature, especially when targeting sensitive organizations or government entities.

• Insider Threat Scenarios:

  • Malicious insiders may encrypt data using symmetric encryption tools or scripts before uploading to cloud storage or sending via email.

• Ransomware Attacks:

  • Ransomware groups often exfiltrate encrypted data prior to encrypting victim systems to leverage double-extortion tactics.

How this Technique is Usually Detected

Detection of exfiltration over symmetric encrypted non-C2 protocols can be challenging due to encryption and use of legitimate protocols. However, multiple detection methods, tools, and indicators of compromise (IoCs) can assist defenders:

• Network Traffic Anomaly Detection:

  • Monitor for unusual patterns in network traffic, such as unexpected high-volume data transfers or periodic outbound connections to unknown external IP addresses or domains.

  • Identify abnormal protocol usage, such as DNS queries with abnormally large payloads or unusual frequency.

• Endpoint Detection and Response (EDR):

  • EDR solutions can detect suspicious encryption activities or unauthorized use of encryption tools (e.g., OpenSSL or GPG) on endpoints.

  • Monitor for execution of unknown scripts or binaries performing encryption operations.

• Data Loss Prevention (DLP):

  • While encrypted data complicates traditional DLP detection, monitoring for unauthorized encryption activities or encryption tool usage can still provide alerts.

• Behavioral Analysis and Machine Learning:

  • Employ machine learning algorithms to detect anomalous behavior in protocol usage or data transfer patterns.

  • Behavioral analysis can detect subtle deviations in normal user or system behavior indicative of data exfiltration activities.

• Indicators of Compromise (IoCs):

  • Unusual DNS queries or HTTP POST requests containing encrypted payloads.

  • Presence of unexpected encryption tools or scripts on endpoints.

  • Large or frequent uploads to cloud storage services from unusual accounts or IP addresses.

Why it is Important to Detect This Technique

Detecting exfiltration over symmetric encrypted non-C2 protocols is critical due to its potential severe impacts on systems and networks:

• Data Loss and Breaches:

  • Undetected exfiltration can result in significant loss of sensitive, proprietary, or personally identifiable information (PII), leading to financial, regulatory, and reputational damage.

• Regulatory and Compliance Issues:

  • Organizations subject to strict compliance standards (e.g., GDPR, HIPAA, PCI DSS) may face legal penalties, fines, or sanctions if data breaches are not detected and reported promptly.

• Operational Disruption:

  • Exfiltration can lead to significant operational disruption, especially if critical intellectual property or business data is stolen.

• Facilitation of Further Attacks:

  • Stolen encrypted data can be leveraged in subsequent attacks, ransomware extortion, blackmail, or espionage activities.

Early detection allows organizations to:

• Minimize data loss and mitigate damage.

• Respond swiftly to contain the breach and prevent further compromise.

• Comply with regulatory requirements by timely reporting and remediation.

• Improve security posture by understanding attacker techniques and adapting defenses accordingly.

Examples

Real-world scenarios demonstrating the use of symmetric encrypted non-C2 protocols for data exfiltration include:

• APT28 (Fancy Bear):

  • Known to use symmetric encryption methods to encrypt data before exfiltration, leveraging common protocols like HTTP(S) and DNS tunneling to evade detection.

  • Tools used include custom malware employing AES encryption routines.

• FIN7 Cybercriminal Group:

  • Utilized symmetric encryption (AES) to encrypt payment card data before exfiltrating it via legitimate cloud storage services and HTTP channels, making detection difficult.

  • Impact included significant financial losses and regulatory penalties for targeted organizations.

• Ransomware Groups (e.g., Maze, REvil):

  • Encrypt sensitive data using symmetric encryption before exfiltrating to attacker-controlled servers or cloud services.

  • Employ double-extortion tactics, threatening victims with public disclosure of stolen data unless ransom is paid.

• Insider Threat Incident:

  • Malicious insiders have been observed encrypting sensitive corporate documents using AES encryption and exfiltrating via personal email or cloud storage platforms.

  • Resulted in intellectual property theft and significant financial and reputational impacts.

These examples highlight the versatility and severity of this technique, underscoring the importance of proactive detection and response strategies.