Standard Encoding

Standard Encoding [T1132.001]

Information

• Name: Standard Encoding

• ID: T1132.001

• Tactics: TA0011

• Technique: T1132

Introduction

Standard Encoding (T1132.001) is a sub-technique within the MITRE ATT&CK framework under the "Data Encoding" technique. Attackers commonly use standard data encoding schemes, such as Base64, hexadecimal, or URL encoding, to obfuscate malicious payloads, scripts, or commands. This obfuscation helps adversaries evade detection by signature-based security solutions, thereby facilitating successful infiltration, persistence, and lateral movement within targeted environments.

Deep Dive Into Technique

Attackers utilizing Standard Encoding typically leverage common encoding schemes to mask malicious data or commands from detection mechanisms. Common encoding methods include:

• Base64 Encoding

  • Converts arbitrary binary data into ASCII text representation.

  • Commonly used to hide malicious payloads in scripts, PowerShell commands, and HTTP traffic.

  • Example: powershell.exe -EncodedCommand <Base64 payload>

• Hexadecimal Encoding

  • Represents binary data using hexadecimal notation.

  • Frequently employed in malware payloads and encoded shellcode.

  • Example: %41%42%43%44 represents the ASCII string "ABCD".

• URL Encoding

  • Converts special characters into percent-encoded format.

  • Commonly used in web-based injection attacks and malicious URLs.

  • Example: %3Cscript%3Ealert(1)%3C%2Fscript%3E represents <script>alert(1)</script>.

Attackers often combine encoding techniques with additional obfuscation methods, such as encryption, compression, or string concatenation, to further complicate analysis and detection. Standard Encoding can be applied at various stages of an attack lifecycle, including initial access, execution, persistence, command-and-control (C2) communications, and data exfiltration.

When this Technique is Usually Used

Standard Encoding is widely utilized by adversaries across multiple attack scenarios and stages, including:

• Initial Access and Delivery

  • Malicious email attachments containing encoded payloads.

  • Encoded scripts or macros embedded in documents to bypass email filters and antivirus solutions.

• Execution and Persistence

  • Encoded PowerShell, VBScript, or JavaScript commands executed directly or via scheduled tasks.

  • Registry-based persistence mechanisms storing encoded commands or payloads.

• Command-and-Control (C2) Communications

  • Encoded HTTP POST requests or responses to evade network security monitoring.

  • Encoded DNS queries used for covert channel communication.

• Data Exfiltration

  • Sensitive data encoded before exfiltration to evade Data Loss Prevention (DLP) tools and network monitoring.

How this Technique is Usually Detected

Detection of Standard Encoding involves multiple methods and tools, including:

• Signature-Based Detection

  • Antivirus and endpoint detection solutions capable of identifying encoded payload signatures.

  • YARA rules specifically designed to detect encoded malicious scripts or binaries.

• Behavioral Analysis

  • Endpoint Detection and Response (EDR) tools monitoring suspicious command-line executions, especially encoded PowerShell commands (-EncodedCommand flag).

  • Anomaly detection systems identifying unusual patterns in encoded network traffic or DNS queries.

• Network Traffic Analysis

  • Network Intrusion Detection Systems (NIDS) and proxies configured to decode Base64, hexadecimal, and URL-encoded traffic to inspect payloads.

  • SSL/TLS interception and deep packet inspection to detect encoded malicious payloads within encrypted channels.

• Log Analysis and SIEM

  • Centralized log analysis and Security Information and Event Management (SIEM) systems correlating encoded command executions and suspicious network activities.

  • Monitoring Windows Event Logs for suspicious encoded command executions via PowerShell, cmd.exe, or scripting engines.

Indicators of Compromise (IoCs)

• Suspicious command-line arguments containing encoded strings (e.g., Base64 payloads).

• Unusual HTTP headers or parameters containing encoded data.

• Encoded DNS queries indicative of covert channel communications.

• Registry entries or scheduled tasks containing encoded script commands.

Why it is Important to Detect This Technique

Early detection of Standard Encoding is crucial due to its widespread use and effectiveness in evading traditional signature-based security measures. Importance of detection includes:

• Preventing Initial Compromise

  • Detecting encoded payloads early can prevent initial malware infection and subsequent exploitation.

• Reducing Dwell Time

  • Early identification of encoded commands or payloads can significantly reduce attacker dwell time, limiting damage and lateral movement.

• Minimizing Data Loss

  • Detecting encoded exfiltration attempts can prevent sensitive data leakage, protecting organizational assets and reputation.

• Enhancing Security Posture

  • Identifying and mitigating encoding-based obfuscation methods strengthens overall security posture and resilience against sophisticated threats.

Examples

Real-world examples and scenarios involving Standard Encoding include:

• Emotet Malware

  • Frequently uses Base64-encoded PowerShell scripts embedded in malicious documents to evade antivirus detection.

  • Example scenario:

    • Victim receives phishing email with malicious Word document.

    • Document triggers macros executing Base64-encoded PowerShell payload.

    • Payload downloads additional malware components, establishing persistence and lateral movement.

• Cobalt Strike Framework

  • Uses Base64 and hexadecimal encoding extensively for payload obfuscation and C2 communications.

  • Example scenario:

    • Attacker deploys encoded payload via phishing or exploit.

    • Encoded commands executed via PowerShell or cmd.exe to establish beaconing and persistence.

    • Encoded HTTP traffic used for stealthy C2 communications, evading network detection.

• Magecart Web Skimming Attacks

  • Attackers inject URL-encoded JavaScript payloads into compromised websites to steal payment card data.

  • Example scenario:

    • Attacker compromises e-commerce website, embedding URL-encoded JavaScript skimmer.

    • Encoded JavaScript collects and exfiltrates sensitive customer data, bypassing basic detection mechanisms.

• DNS Tunneling Attacks

  • Attackers encode data within DNS queries to create covert communication channels.

  • Example scenario:

    • Malware encodes data in hexadecimal or Base32 format within DNS request subdomains.

    • Encoded DNS traffic bypasses firewall and network monitoring, allowing stealthy data exfiltration or C2 communication.