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Introduction:
Traditional Portable Executable (PE) analysis fails against a rising tide of malicious scripts, shortcut files, and polyglot payloads – attackers now weaponize formats like .lnk, Python, PowerShell, and JavaScript to bypass security defenses. Non-binary analysis fills this gap by applying static reverse-engineering techniques to unconventional file types, enabling defenders to dissect threats that never touch classic executables.
Learning Objectives:
- Analyze malicious .lnk, PowerShell, JavaScript, and Python files using static analysis and deobfuscation methods.
- Utilize Radare2 for advanced reverse engineering of non‑traditional executable formats and embedded shellcode.
- Detect and mitigate fileless and script‑based attacks across Windows and Linux environments through proactive threat hunting.
You Should Know:
1. Understanding Non-Binary Formats: The Hidden Attack Surface
Attackers increasingly rely on file types that are rarely subjected to deep inspection. Shortcut (.lnk) files can embed PowerShell commands, Python scripts can be compiled into bytecode or wrapped in executables, and JavaScript can run via Windows Script Host. Traditional antivirus often scans only PE headers, leaving these vectors open. Step‑by‑step guide to identify such files:
– On Linux: Use `file suspicious.lnk` to detect the file type; `strings suspicious.lnk | head -20` reveals human‑readable content, often showing embedded commands.
– On Windows PowerShell: `Get-Content suspicious.lnk -Encoding Unicode | Select-String -Pattern “powershell|cmd|rundll32″` extracts cleartext command lines.
– For Python scripts: `python -m py_compile malicious.py` followed by `strings malicious.pyc` may expose hidden imports. Always analyse in an isolated sandbox (REMnux or FlareVM).
- Analyzing Malicious .LNK Files with PowerShell and Radare2
.LNK files are more than shortcuts – they can store target paths, working directories, and arguments that execute malicious code. A typical attack uses an .lnk that runspowershell.exe -EncodedCommand .... Step‑by‑step extraction and analysis:
– Extract using PowerShell (Windows):
$lnk = New-Object -ComObject WScript.Shell
$shortcut = $lnk.CreateShortcut("C:\path\to\malicious.lnk")
Write-Host "Target: " $shortcut.TargetPath
Write-Host "Args: " $shortcut.Arguments
– Binary inspection with Radare2 (Linux):
radare2 -A malicious.lnk Load and analyze [bash]> izz List all strings – look for "powershell", "cmd", or Base64 [bash]> / powershell Search for command patterns
– Manual hex dump: `hexdump -C malicious.lnk | grep -i “powershell”` – the argument block often appears after the `COMMAND_LINE_ARGUMENTS` structure (offset 0x14).
- Static Analysis of PowerShell and Python Script Payloads
Malicious scripts are usually heavily obfuscated – variable name substitution, string concatenation, and Base64 encoding. Step‑by‑step deobfuscation:
– PowerShell: Enable script block logging (Windows Event ID 4104). For static analysis, copy the script into a text editor and replace common obfuscation patterns:
Example: remove backticks and replace -join fragments $obf = (Get-Content malicious.ps1) -replace "<code>"","" $obf -match 'powershell.-e' Detects encoded commands
Use `Invoke-Obfuscation` detection: `Invoke-Obfuscation -ScriptBlock $raw -Decode` from the PowerSploit framework.
– Python: Extract AST to flatten obfuscation:
import ast
with open('malicious.py') as f:
tree = ast.parse(f.read())
print(ast.unparse(tree)) Python 3.9+ unparse restores readable code
For encoded payloads, search for `exec()` or `eval()` calls:grep -n “exec|eval” malicious.py`.
4. Leveraging Radare2 for Non-Binary Reverse Engineering
Radare2 is not limited to PE/ELF – it can dissect shellcode, raw binaries, and even script wrappers. Step‑by‑step configuration for non‑binary analysis:
– Install radare2 (Linux/macOS/WSL): `git clone https://github.com/radareorg/radare2 && cd radare2 && sys/install.sh`
– Analyze a malicious JavaScript payload embedded in a .lnk: extract the JavaScript string with strings, save as payload.js, then load into radare2:
r2 -a x86 -b 32 payload.js Force architecture if code is shellcode [bash]> e asm.emu=true Enable emulation [bash]> pd 20 Disassemble first 20 lines
– For PowerShell scripts, use radare2 to find encoded commands: `r2 -c “izz | grep -i ‘base64′” payload.ps1` – then decode manually or with echo "encoded" | base64 -d.
– Analyze .lnk files for embedded shellcode: `r2 -A malicious.lnk` followed by `pdf @ sym._` to see function calls; shellcode often resides in the `COMMAND_LINE` area.
5. Practical Exercises from Blackstorm Security’s Training Approach
The Blackstorm Security training emphasizes hands‑on labs with real malicious samples in non‑PE formats. A typical lab workflow:
– Setup isolated environment: Use VirtualBox with FlareVM (Windows) and REMnux (Linux). Disable network adapters or use a host‑only network.
– Identify sample formats: Run `Detect-It-Easy` (DIE) or `file` to recognise .lnk, .ps1, .py, .js. Example:
diec -e sample.lnk Show entropy and structural info
– Extract indicators with YARA: Write a rule to match common .lnk malicious patterns (e.g., high number of arguments, presence of powershell.exe). Example YARA rule:
rule Lnk_PowerShell
{
strings:
$ps = "powershell.exe" ascii wide
$enc = "EncodedCommand" ascii
condition:
$ps and $enc
}
– Submit to static analysis pipeline: Use strings, capabilities, and `peframe` (for embedded resources). For Python bytecode, `uncompyle6 malicious.pyc` recovers source.
- Threat Hunting for Script-Based Malware in Enterprise Networks
Proactive detection requires logging and correlation. Step‑by‑step configuration for Windows environments:
– Enable PowerShell logging via Group Policy (Admin Templates → Windows Components → Windows PowerShell):
– Turn on Module Logging, Script Block Logging, and Transcription.
– Collect events with Sysmon (Event ID 1 – process creation; Event ID 3 – network connection). Command to install and configure:
.\Sysmon64.exe -accepteula -i sysmon-config.xml
– Monitor suspicious command lines using Windows Event Forwarding (WEF) or a SIEM. Example KQL (Sentinel) for .lnk execution:
DeviceProcessEvents | where FileName == "explorer.exe" and ProcessCommandLine contains ".lnk"
– Linux threat hunting for Python/JS malware: Audit execve syscalls:
sudo auditctl -a always,exit -F arch=b64 -S execve -k script_exec ausearch -k script_exec | grep -E "python|node|powershell"
7. Mitigation and Hardening Against Non-Binary Attacks
Prevent execution of malicious scripts and shortcut abuse using built‑in controls:
– Windows Defender ASR rules (Attack Surface Reduction): Block JavaScript/VBScript from launching downloaded executable content. Deploy via Intune or Group Policy:
Add-MpPreference -AttackSurfaceReductionRules_Ids 3B576869-A4EC-41E0-AEE4-BD20A57FA57E -AttackSurfaceReductionRules_Actions Enabled
– AppLocker to whitelist allowed scripts: Create rules for PowerShell, Python, and .lnk execution paths.
– Constrained Language Mode (PowerShell) – prevents arbitrary code invocation:
$ExecutionContext.SessionState.LanguageMode = "ConstrainedLanguage"
– Disable .lnk execution from USB via Group Policy (Administrative Templates → System → Removable Storage Access). Also, enforce LSA protection to block process injection from script hosts.
What Undercode Say:
- Non‑PE formats are the new frontier for malware delivery – defenders must expand analysis skills beyond traditional binaries.
- Radare2 and native system tools (PowerShell, string extraction, YARA) form a powerful, low‑cost stack for non‑binary reverse engineering.
- Proactive hardening (ASR, AppLocker, script logging) drastically reduces the attack surface for fileless and script‑based threats.
Prediction:
By 2027, over 60% of enterprise breaches will originate from non‑binary attacks (.lnk, JS, VBA, Python) as adversaries avoid PE detection. This shift will force SOC teams to integrate script analysis into their daily workflows, driving demand for training like Blackstorm’s “Non‑Binary Analysis”. Automated static analysis tools will evolve to decode polyglot files, but human expertise in radare2 and manual deobfuscation will remain critical for zero‑day threats. Expect an increase in blue‑team exercises focusing on shortcut files and script‑based persistence, as well as new regulatory guidance mandating script block logging across all endpoints.
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