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Version: VAST v3.1


A module creates a namespace for type definitions#type-construction, pipelines, and taxonomy elements in single YAML file.

Work in Progress

While you can already read type definitions, it is unfortunately not yet possible write them in the same syntax. We are working towards closing this gap, as tracked by the corresponding roadmap item.

Type Definition Rules

All defined type names and aliases share one global identifier namespace. Introducing a new type definition or alias adds a symbol to this namespace. The following rules exist to make manipulation of the namespace manageable:

  • VAST processes all directories of the vast.module-dirs option in order, creating a union of all type definitions.

  • Within a specified module directory, all type definitions must be unique, i.e., no types can have the same name.

  • Across directories, later definitions can override existing ones from previous directories. This allows users to adapt existing types by providing an alternate definition in a separate module directory.

  • Resolving aliases to custom types follows a 2-phase lookup, which makes it possible to use a custom type and define it afterwards in the module file. The 2-phase lookup only works within a module directory.


VAST processes all directories recursively. This means you are free to split the content over a directory structure of your choice.

Module Directory Lookup

VAST ships with modules containing type definitions and aliases for common formats, such as Zeek or Suricata logs. Pre-installed modules reside in <datadir>/vast/modules, and additional search paths for user-provided modules can be set in the configuration file vast.yaml by adjusting the vast.module-dirs option.

VAST looks at module directories in the following order:

  1. <datadir>/vast/module for system-wide module files bundled with VAST, where <datadir> is the platform-specific directory for data files, e.g., <install-prefix>/share.

  2. <sysconfdir>/vast/modules for system-wide configuration, where <sysconfdir> is the platform-specific directory for configuration files, e.g., <install-prefix>/etc.

  3. ~/.config/vast/modules for user-specific configuration. VAST respects the XDG base directory specification and its environment variables.

  4. An ordered, comma-separated list of directories passed using --module-dirs=path/to/modules on the command line. This corresponds to the option vast.module-dirs.

Changing VAST modules

We recommend to avoid making changes to module files in <datadir>/vast/modules, as this can break updates to VAST. If you need to make adaptations of builtin types, you can modify them in your own module directory with the help of record type operations.