t1055-proc-injctn-sysmon

name	t1055-proc-injctn-sysmon
description	Detect process injection techniques (T1055) including classic DLL injection, process hollowing, and APC injection by analyzing Sysmon events for cross-process memory operations, remote thread creation, and anomalous DLL loading patterns.
domain	cybersecurity
subdomain	threat-hunting
tags	["threat-hunting","process-injection","sysmon","mitre-t1055","defense-evasion","dll-injection","process-hollowing"]
version	1.0
author	mahipal
license	Apache-2.0
d3fend_techniques	["Executable Denylisting","Execution Isolation","File Metadata Consistency Validation","Content Format Conversion","File Content Analysis"]
nist_csf	["DE.CM-01","DE.AE-02","DE.AE-07","ID.RA-05"]

Detecting T1055 Process Injection with Sysmon

When to Use

• When hunting for defense evasion techniques that hide malicious code inside legitimate processes
• After EDR alerts for suspicious cross-process memory access or remote thread creation
• When investigating malware that injects into svchost.exe, explorer.exe, or other system processes
• During purple team exercises testing detection of process injection variants
• When validating Sysmon configuration coverage for injection detection

Prerequisites

• Sysmon deployed with comprehensive configuration capturing Events 1, 7, 8, 10, 25
• Event ID 8 (CreateRemoteThread) enabled for remote thread detection
• Event ID 10 (ProcessAccess) configured with appropriate access mask filters
• Event ID 7 (ImageLoaded) for DLL injection detection
• Event ID 25 (ProcessTampering) for process hollowing on Sysmon 13+
• SIEM platform for correlation and alerting

Workflow

1. Monitor CreateRemoteThread (Event 8): Detect when one process creates a thread in another process's address space. This is the primary indicator of classic DLL injection and shellcode injection.
2. Analyze ProcessAccess (Event 10): Track cross-process handle requests with PROCESS_VM_WRITE (0x0020), PROCESS_VM_OPERATION (0x0008), and PROCESS_CREATE_THREAD (0x0002) access rights. Legitimate processes rarely need these on other processes.
3. Detect Anomalous DLL Loading (Event 7): Identify DLLs loaded from unusual paths (user temp directories, download folders) into system processes.
4. Hunt Process Hollowing (Event 25): Sysmon 13+ generates ProcessTampering events when the executable image in memory diverges from what was mapped from disk -- a hallmark of process hollowing (T1055.012).
5. Correlate with Process Creation: Link injection events to the originating process creation (Event 1) to build the full attack chain from initial execution to injection.
6. Filter Known-Good Cross-Process Activity: Exclude legitimate software that performs cross-process operations (debuggers, AV products, accessibility tools, RMM agents).
7. Map to ATT&CK Sub-Techniques: Classify detected injection as classic injection (T1055.001), PE injection (T1055.002), thread execution hijacking (T1055.003), APC injection (T1055.004), thread local storage (T1055.005), process hollowing (T1055.012), or process doppelganging (T1055.013).

Key Concepts

Concept