Window’s Infinity Edge - HackTheBox Challenge Writeup

Challenge Information

Challenge Description

An APT group has successfully breached the company and deployed custom malware implants across multiple systems. The security team has identified and remediated the infections using advanced AntiVirus X. However, one server continues to exhibit suspicious network traffic despite appearing clean during the remediation process.

Objective: Analyze the forensic artifacts from the compromised server to identify what the antivirus may have missed—likely a sophisticated persistence mechanism or hidden implant that evaded standard detection.

Solution Overview

This challenge requires deep Windows forensics analysis to uncover persistence mechanisms that bypass traditional antivirus scanning. The “clean” system actually contains remnants of the APT tooling that weren’t detected by the standard remediation process.

Key Steps

1. Initial Analysis

Begin by examining the forensic artifacts provided in the challenge:

# List available forensic data
ls -la forensic_data/

# Check for common Windows artifacts
file forensic_data/*

2. Windows Registry Analysis

The persistence mechanism is likely hidden in Windows registry hives:

# Extract and parse SAM, SYSTEM, SOFTWARE hives
# Look for Run, RunOnce, and other persistence locations
regripper -r forensic_data/SYSTEM -p services
regripper -r forensic_data/SOFTWARE -p userassist
regripper -r forensic_data/SOFTWARE -p shimcache

3. Browser and User Artifacts

Examine user profiles for suspicious activity:

# Check browser history and cache
# Analyze Recently Used files
# Review Prefetch files for execution patterns
strings forensic_data/NTUSER.DAT | grep -i suspicious

4. File System Analysis

Search for hidden or obfuscated malware:

# Look for alternate data streams (ADS)
# Search for recently modified files
# Check temp directories and AppData folders
find forensic_data -type f -name "*.exe" -o -name "*.dll"

5. Memory and Network Artifacts

Correlate suspicious network traffic with process execution:

# Analyze network connections logs
# Review DNS query logs
# Cross-reference with process artifacts
cat forensic_data/network_logs | grep -v "standard_traffic"

Tools Used

• regripper — Windows registry parsing and analysis
• strings — Binary file analysis and artifact extraction
• volatility — Memory forensics (if memory dump available)
• FTK Imager / Autopsy — Forensic imaging and timeline analysis
• Eric Zimmerman Tools — Timeline and registry analysis utilities

Key Learnings

1. Antivirus Gap: Commercial antivirus solutions may miss sophisticated persistence mechanisms, especially custom-compiled implants that don’t match known signatures.

2. Defense in Depth: A “clean” system requires verification through multiple forensic techniques, not just antivirus scans. Look beyond obvious malware to registry modifications, scheduled tasks, and WMI event subscriptions.

3. APT Sophistication: Advanced groups often implement multi-layered persistence—if one method is detected, others remain active. Check:

   • Registry Run keys and boot executables
   • Scheduled tasks and WMI subscriptions
   • Startup folders and shell extensions
   • Browser extensions and BHOs
   • Windows services with suspicious descriptions

4. Artifact Correlation: Network traffic anomalies should be correlated with execution artifacts. Suspicious outbound connections often map to specific processes in timeline analysis.

5. Evidence Preservation: Always maintain a clean copy of forensic evidence and work on isolated systems to avoid contamination.

Flag

HTB{<redacted>}

Note: This writeup reflects the challenge structure based on available solve notes. For complete technical details, reproduce the analysis on the actual challenge environment with the provided forensic artifacts.