evtxecmd-maps

name	evtxecmd-maps
description	Understand, author, and validate EvtxECmd map files that normalize Windows event log EventData into first-class CSV/JSON columns.

EvtxECmd Maps

This skill describes how an agent should understand, create, and validate EvtxECmd map files in this repository (the files under evtx/Maps/ ending in .map). Map files are YAML documents that tell EvtxECmd how to extract values from an event's EventData (and optionally System) elements and project them into a small set of standardized columns (UserName, RemoteHost, ExecutableInfo, PayloadData1 … PayloadData6).

A starter template is included alongside this skill at assets/!Channel-Name_Provider-Name_EventID.template. Always start a new map by copying that template rather than writing one from scratch.

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1. What a map file is

A map is a YAML file whose filename and four header fields together identify a specific event:

Header field	Required	Meaning
Author	optional	Name / contact of the map author.
Description	required	Human description of the event. No trailing period.
EventId	required	The integer Event ID (matches <EventID> in the XML).
Channel	required	The exact value from the <Channel> element.
Provider	required	The exact value of <Provider Name="…">. Mandatory since December 2020 to disambiguate event IDs that are reused by multiple providers.

Below the header is a Maps: sequence describing how to build each output column, and an optional Lookups: sequence defining value-translation tables.

The map is matched to an event when all of Channel, Provider, and EventId match the event's XML. The filename does not select the map, but it must follow the naming rules below so duplicates can be detected.

Filename rules

Format:

<Channel-Name>_<Provider-Name>_<EventID>.map

• Underscores (_) separate the three elements.
• Hyphens (-) replace any spaces, slashes, or special characters within Channel and Provider names.
• The extension must be .map (lowercase is used throughout the repo).
• Filenames may be long; that is expected.

Example — for Channel = Microsoft-Windows-TaskScheduler/Operational, Provider = Microsoft-Windows-TaskScheduler, EventID = 201:

Microsoft-Windows-TaskScheduler-Operational_Microsoft-Windows-TaskScheduler_201.map

To override an existing default map without losing your changes on update, prepend 1_ to the filename. Maps load alphabetically, so the 1_… copy wins:

1_Security_Microsoft-Windows-Security-Auditing_4624.map

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2. Authoring workflow

1. Get real XML for the event. Run EvtxECmd against a sample log to dump the records to XML:

   EvtxECmd.exe -f <your eventlog.evtx> --xml c:\temp\xml
   

   Open the resulting XML and locate the event of interest. Note the values of <Channel>, <Provider Name="…">, and <EventID>, and inspect the <EventData> block for the <Data Name="…"> fields you want to surface.

2. Copy the template. Start from assets/!Channel-Name_Provider-Name_EventID.template (also located at evtx/Maps/!Channel-Name_Provider-Name_EventID.template). Save it under evtx/Maps/ using the filename rules above.

3. Fill in the header. Set Author, Description, EventId, Channel, Provider. There must be no blank line between Provider: and Maps:.

4. Define each Maps: entry. Each entry produces one output column:

   • Property: — must be exactly one of UserName, RemoteHost, ExecutableInfo, PayloadData1, PayloadData2, PayloadData3, PayloadData4, PayloadData5, PayloadData6. Use this exact casing (e.g. UserName, never Username).
   • PropertyValue: — the rendered string, with %name% placeholders for every variable referenced in Values.
   • Values: — list of { Name, Value } pairs. Name must match a %name% placeholder. Value is an XPath expression, normally "/Event/EventData/Data[@Name=\"<FieldName>\"]". You can also index by position: /Event/EventData/Data[1] (first <Data> node), [2], etc.
   • (optional, on a entry) — a regex applied to the XPath result to extract a substring. Example: .

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3. Reference structure

This is the canonical shape of a map. The full template is in assets/!Channel-Name_Provider-Name_EventID.template.

Author: Your name <[e-mail]>
Description: Short description of the event
EventId: 4624
Channel: Security
Provider: Microsoft-Windows-Security-Auditing
Maps:
  -
    Property: UserName
    PropertyValue: "%domain%\\%user%"
    Values:
      -
        Name: domain
        Value: "/Event/EventData/Data[@Name=\"SubjectDomainName\"]"
      -
        Name: user
        Value: "/Event/EventData/Data[@Name=\"SubjectUserName\"]"
  -
    Property: PayloadData1
    PropertyValue: "LogonType %LogonType%"
    Values:
      -
        Name: LogonType
        Value: "/Event/EventData/Data[@Name=\"LogonType\"]"
Lookups:
  -
    Name: LogonType
    Default: Unknown
    Values:
        2: Interactive
         
         
         

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4. Validating a map file

Before committing a new or modified map, an agent must validate it. CI runs the same check via .github/workflows/verify.yml, which invokes yamllint evtx/Maps using the rules in the repository's .yamllint. The .yamllint yaml-files list explicitly includes *.map, so map files are linted as YAML.

4.1 Structural / lint validation

Run from the repository root:

pip install yamllint
yamllint evtx/Maps

To target only the file you are editing:

yamllint evtx/Maps/<your-file>.map

The repo's .yamllint enforces (failures, not warnings):

• braces, brackets, colons, commas, hyphens, indentation — correct YAML punctuation and 2-space block indentation consistent with neighbors.
• empty-lines — no stray blank lines (in particular, no blank line between Provider: and Maps:).
• key-duplicates — every key in a mapping must be unique. In a map file, this means each Property: value (UserName, PayloadData1, …) may appear at most once in Maps:, and each Name: inside a single Values: list must be unique.
• trailing-spaces — no spaces at end of line.
• new-line-at-end-of-file — file must end with exactly one \n.

comments, comments-indentation, and truthy are configured as warnings and will not fail CI, but should still be addressed when easy.

If yamllint evtx/Maps exits 0, the structural check passes.

4.2 Semantic checks the linter cannot catch

After yamllint is clean, also confirm by inspection:

• Filename matches headers. Filename is <Channel>_<Provider>_<EventId>.map with /, spaces, and special chars in Channel/Provider replaced by -. The Channel/Provider/EventId in the filename match the corresponding header fields exactly.
• All required headers are present and non-placeholder: Description, EventId, Channel, Provider. Description has no trailing period.
• Property values are from the allowed set with exact casing: UserName, RemoteHost, ExecutableInfo, PayloadData1–PayloadData6.
• No duplicate Property entries within Maps:.
• Every %name% placeholder in PropertyValue has a matching Name entry in that block's Values:, and vice versa (no orphan variables, no unresolved placeholders).
• XPaths are quoted with "…" and embedded " escaped as \". Backslashes in PropertyValue strings are doubled (\\).
• Lookups: is a single top-level key (all lookup tables are nested under it), each with Name, Default, and Values of integer/string pairs. A lookup Name matching a Values Name is what triggers translation.
• Footer is present: a # Documentation: block (URLs or N/A) and a # Example Event Data: block containing a real, sanitized XML sample.
• File ends with a trailing newline.
• Test on real data: run EvtxECmd against a sample .evtx and confirm the produced CSV/JSON columns are populated correctly.

If any of the above fails, fix the map and re-run yamllint evtx/Maps until it is clean.

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5. Quick checklist for an agent creating a new map

1. Dump the source .evtx to XML and locate the target event.
2. Copy assets/!Channel-Name_Provider-Name_EventID.template to evtx/Maps/<Channel>_<Provider>_<EventId>.map.
3. Set Author, Description, EventId, Channel, Provider.
4. Replace the template's Maps: blocks with Property entries that match the actual event; delete unused PayloadDataN blocks.
5. Add Lookups: only if codes need translating; keep all tables under one Lookups: key.
6. Replace the template footer with real # Documentation: URLs and a sanitized # Example Event Data: XML sample.
7. Ensure the file ends with a single newline and contains no trailing whitespace and no blank line between Provider: and Maps:.
8. Run yamllint evtx/Maps and fix any errors.
9. Run the map against real data with EvtxECmd and confirm output columns.