Detecting T1055 Process Injection With Sysmon

What it does

When your agent uses it

• Hunting defense-evasion activity that hides code inside legitimate processes
• Investigating an EDR alert on suspicious cross-process access
• Validating Sysmon coverage for injection detection

Example prompts

• “/detecting-t1055-process-injection-with-sysmon”

Requirements

• Python 3

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

1. 1Monitor CreateRemoteThread (Event 8): Detect when one process creates a thread in another process's address space. This is the primary…
2. 2Analyze ProcessAccess (Event 10): Track cross-process handle requests with PROCESS_VM_WRITE (0x0020), PROCESS_VM_OPERATION (0x0008), and…
3. 3Detect Anomalous DLL Loading (Event 7): Identify DLLs loaded from unusual paths (user temp directories, download folders) into system…
4. 4Hunt Process Hollowing (Event 25): Sysmon 13+ generates ProcessTampering events when the executable image in memory diverges from what was…
5. 5Correlate with Process Creation: Link injection events to the originating process creation (Event 1) to build the full attack chain from…
6. 6Filter Known-Good Cross-Process Activity: Exclude legitimate software that performs cross-process operations (debuggers, AV products…
7. 7Map to ATT&CK Sub-Techniques: Classify detected injection as classic injection (T1055.001), PE injection (T1055.002), thread execution…

What it can do on your machine

Read from SKILL.md and the folder at commit 54a7988. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 2 files in scripts/ (Python), which the agent can run.

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Detecting T1055 Process Injection With Sysmon loads about 2k tokens when it runs, and up to ~4.2k if it reads all its reference files. Until then it costs about 124 tokens; SKILL.md has 550 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~124

When it runs · the whole SKILL.md, loaded when a task matches

~2k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~4.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from mukul975/Anthropic-Cybersecurity-Skills at commit 54a7988, republished under its Apache-2.0 licence (© mukul975). 550 words, ~1,962 tokens.

name

detecting-t1055-process-injection-with-sysmon

description

Detect process injection techniques (T1055) - including DLL injection, process hollowing, and APC injection - by analyzing Sysmon Event IDs 1, 7, 8, 10, and 25 for cross-process memory operations, remote thread creation, and anomalous DLL loads. Use when hunting defense-evasion activity that hides code inside legitimate processes, investigating an EDR alert on suspicious cross-process access, or validating Sysmon coverage for injection detection.

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

mitre_attack

T1055.001, T1055.002, T1055.003, T1055.012

index=sysmon EventCode=8
| where SourceImage!=TargetImage
| where NOT match(SourceImage, "(?i)(csrss|lsass|services|svchost|MsMpEng|SecurityHealthService|vmtoolsd)\.exe$")
| eval suspicious=if(match(TargetImage, "(?i)(svchost|explorer|lsass|winlogon|csrss|services)\.exe$"), "high_value_target", "normal_target")
| where suspicious="high_value_target"
| table _time Computer SourceImage SourceProcessId TargetImage TargetProcessId StartFunction NewThreadId

index=sysmon EventCode=10
| where SourceImage!=TargetImage
| where match(GrantedAccess, "(0x1FFFFF|0x1F3FFF|0x143A|0x0040)")
| where match(TargetImage, "(?i)(lsass|svchost|explorer|winlogon)\.exe$")
| where NOT match(SourceImage, "(?i)(MsMpEng|csrss|services|svchost|taskmgr|procexp)\.exe$")
| table _time Computer SourceImage TargetImage GrantedAccess CallTrace

DeviceEvents
| where Timestamp > ago(7d)
| where ActionType == "CreateRemoteThreadApiCall"
| where InitiatingProcessFileName !in~ ("csrss.exe", "lsass.exe", "services.exe", "svchost.exe")
| where FileName in~ ("svchost.exe", "explorer.exe", "lsass.exe", "winlogon.exe")
| project Timestamp, DeviceName, InitiatingProcessFileName, InitiatingProcessCommandLine,
    FileName, ProcessCommandLine

title: Process Injection via CreateRemoteThread into System Process
status: stable
logsource:
    product: windows
    category: create_remote_thread
detection:
    selection:
        TargetImage|endswith:
            - '\svchost.exe'
            - '\explorer.exe'
            - '\lsass.exe'
            - '\winlogon.exe'
    filter_legitimate:
        SourceImage|endswith:
            - '\csrss.exe'
            - '\lsass.exe'
            - '\services.exe'
            - '\MsMpEng.exe'
    condition: selection and not filter_legitimate
level: high
tags:
    - attack.defense_evasion
    - attack.t1055

Hunt ID: TH-INJECT-[DATE]-[SEQ]
Host: [Hostname]
Source Process: [Injecting process path]
Source PID: [Process ID]
Target Process: [Target process path]
Target PID: [Process ID]
Injection Type: [DLL/Shellcode/Hollowing/APC]
Sysmon Events: [Event IDs triggered]
Access Mask: [Granted access value]
Risk Level: [Critical/High/Medium/Low]
ATT&CK Sub-Technique: [T1055.xxx]

© mukul975, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 7 other files (scripts, references, assets) in skills/detecting-t1055-process-injection-with-sysmon of mukul975/Anthropic-Cybersecurity-Skills.

• SKILL.md
• LICENSE
• assets/template.md
• references/api-reference.md
• references/standards.md
• references/workflows.md
• scripts/agent.py
• scripts/process.py

Open the folder on GitHubat commit 54a7988