Non-Standard Encoding (T1132.002)
Non-Standard Encoding [T1132.002]
Last updated
Non-Standard Encoding [T1132.002]
Last updated
Name: Non-Standard Encoding
ID: T1132.002
Tactics:
Technique:
Non-Standard Encoding (sub-technique T1132.002) is part of the MITRE ATT&CK framework under the parent technique "Data Encoding" (T1132). This sub-technique describes adversaries' use of uncommon or customized encoding schemes to obfuscate or conceal malicious payloads, scripts, commands, or data transfers. Attackers employ non-standard encoding methods to evade detection mechanisms, bypass security controls, and complicate forensic analysis. By leveraging encoding schemes not typically recognized or expected by standard monitoring tools, adversaries can effectively hide their activities and maintain stealth within compromised environments.
Adversaries utilize Non-Standard Encoding through various methods to evade detection and complicate analysis. Common execution methods and mechanisms include:
Custom Encoding Algorithms:
Attackers may develop proprietary encoding algorithms that differ significantly from widely recognized standards such as Base64 or hexadecimal encoding.
Custom algorithms can involve character substitution, bitwise operations, XOR encoding, or arbitrary transformations of data.
Obfuscated Scripts and Payloads:
Malicious scripts (e.g., PowerShell, Python, JavaScript) may utilize non-standard character encodings or obscure encoding formats to bypass signature-based detection.
Encoded payloads are decoded at runtime, making static analysis challenging.
Binary Data Manipulation:
Attackers may encode binary payloads using custom encoding methods to evade antivirus and intrusion detection systems.
Techniques include XOR encoding, bit shifting, or custom compression algorithms.
Protocol-Level Encoding:
Attackers may encode command-and-control (C2) communications using unusual or custom protocols and encoding schemes to evade packet inspection tools.
Examples include encoding payloads within HTTP headers, cookies, DNS queries, or other protocol fields.
Steganography and Data Concealment:
Embedding encoded data within seemingly benign files (images, documents, multimedia) using non-standard encoding to bypass content inspection mechanisms.
This sub-technique typically appears in multiple stages of cyber attacks, including:
Initial Access and Delivery:
Attackers encode malicious payloads within phishing emails, attachments, or web downloads to evade email gateways and endpoint protection.
Execution and Persistence:
Encoded scripts or binaries are deployed to compromised systems to avoid detection by endpoint security tools and antivirus software.
Command-and-Control (C2) Communications:
Attackers encode outbound and inbound communications between compromised hosts and C2 servers to evade network monitoring and detection systems.
Data Exfiltration:
Attackers leverage custom encoding schemes to conceal sensitive data being exfiltrated, making it difficult for data loss prevention (DLP) solutions and network monitoring tools to detect and interpret the stolen information.
Defense Evasion:
Non-standard encoding is primarily used as a defense evasion tactic to bypass signature-based detection, heuristic analysis, and behavioral monitoring tools.
Detection of Non-Standard Encoding relies on multiple methods, tools, and indicators of compromise (IoCs):
Behavioral Analysis:
Monitoring for unusual script execution patterns, such as PowerShell or scripting engines decoding payloads at runtime.
Detecting anomalous behavior in processes involving unexpected decoding routines or data transformations.
Network Traffic Analysis:
Identifying abnormal or suspicious protocol communications, such as unusual HTTP headers, DNS queries, or encoded payloads within standard protocols.
Using deep packet inspection tools (e.g., Zeek, Suricata) to detect protocol anomalies and encoded data streams.
Endpoint Detection and Response (EDR):
Leveraging EDR solutions to detect processes performing unusual encoding or decoding operations, particularly involving uncommon or unknown algorithms.
Monitoring command-line arguments and scripts for suspicious encoding operations or decoding routines.
SIEM and Log Analysis:
Correlating logs from multiple sources (endpoint, network, application) to identify unusual encoding activities or decoding operations.
Setting up alerts based on known suspicious behaviors or encoding-related anomalies.
File and Payload Analysis:
Utilizing sandbox analysis and reverse-engineering tools to detect and analyze encoded payloads or scripts.
Identifying encoded data within seemingly benign files through static and dynamic analysis.
Indicators of compromise (IoCs) may include:
Suspicious command-line arguments involving decoding functions or unusual parameters.
Unusual file artifacts or scripts containing custom decoding routines.
Abnormal network communications involving encoded or obfuscated protocol fields.
Detecting Non-Standard Encoding is critical due to its significant impacts on systems and networks, including:
Evasion of Security Controls:
Attackers bypass traditional signature-based antivirus, intrusion detection/prevention systems, and content filtering solutions, allowing malicious payloads to execute undetected.
Persistent Compromise:
Encoded payloads and scripts facilitate persistent access, enabling attackers to maintain long-term footholds within compromised environments.
Data Exfiltration and Theft:
Encoded data exfiltration can go unnoticed by network monitoring tools, leading to sensitive data loss and compliance violations.
Increased Complexity of Incident Response:
Non-standard encoding complicates forensic analysis, incident response, and threat hunting efforts, delaying detection and remediation.
Potential for Further Attacks:
Successful encoding evasion techniques enable attackers to establish persistent backdoors, deploy ransomware, or conduct lateral movement, significantly increasing the potential damage and scope of the attack.
Early detection and response to Non-Standard Encoding techniques significantly reduce the potential impact, limit attackers' persistence, and simplify incident response efforts.
Real-world examples of Non-Standard Encoding include:
APT29 (Cozy Bear):
Utilized custom encoding and obfuscation techniques within PowerShell scripts during the SolarWinds supply-chain compromise.
Encoded malicious payloads and scripts to evade endpoint and network detection, enabling persistent access and lateral movement within targeted organizations.
FIN7 Threat Group:
Employed custom encoding routines within JavaScript payloads delivered via phishing emails to bypass email filtering solutions and endpoint antivirus software.
Encoded payloads were decoded at runtime, leading to successful compromise and data theft from financial institutions and retail organizations.
Emotet Malware:
Utilized custom encoding and obfuscation within malicious documents and macros to evade antivirus detection.
Encoded payloads were delivered via email attachments, enabling widespread infection and subsequent malware deployment (e.g., TrickBot, Ryuk ransomware).
Cobalt Strike Framework:
Attackers frequently customize encoding schemes within Cobalt Strike payloads and beacon communications to evade network detection and endpoint defenses.
Custom encoding helps attackers maintain stealthy command-and-control communications and persistent access.
DNS Tunneling Attacks:
Adversaries encode data within DNS queries and responses using custom encoding schemes to evade network monitoring and firewall rules.
Encoded DNS tunneling has been leveraged to exfiltrate sensitive data from compromised networks undetected.
These examples highlight the diversity of encoding techniques, the variety of tools leveraged by attackers, and the significant impacts resulting from successful deployment of non-standard encoding methods.