Rules

Syntax

The syntax for the rules files is:

- action: <string,mandatory>
  description: <string>
  actionner: <string,mandatory>
  continue: <bool>
  ignore_errors: <bool>
  parameters:
    <string>: <string>
    <string>:
      - <string>
      - <string>
    <string>:
      <string>: <string>
      <string>: <string>

- rule: <string,mandatory>
  description: <string>
  match:
    rules:
      - <string>
      - <string>
    priority: <string>
    tags:
      - <string>, <string>, <string>
      - <string>, <string>
    output_fields:
      - <string>=<string>, <string>=<string>
      - <string>!=<string>, <string>=<string>
  continue: <bool>
  dry_run: <bool>
  actions:
    - action: <string,mandatory>
    - action: <string,mandatory>
      description: <string>
      actionner: <string,mandatory>
      continue: <bool>
      ignore_errors: <bool>
      parameters:
        <string>: <string>
        <string>:
          - <string>
          - <string>
        <string>:
          <string>: <string>
          <string>: <string>
  notifiers:
    - <string>
    - <string>

The rules files contain 2 types of blocks:

• action: defines an action that can be reused by different rules
• rule: defines a rule to match with events and run actions

Action

For the action block, the settings are:

• action: (mandatory) name of action to trigger
• description: description of the action (for user only)
• actionner: name of the actionner to use
• continue: if true, no more action are applied after this one (each actionner has its own default value).
• ignore_errors: if true, ignore the errors and avoid to stop at this action.
• parameters: key:value map of parameters for the action. value can be a string, an array (slice) or a map.

Rule

For the rule block, the settings are:

• rule: (mandatory) Name of your rule
• description: description of the action (for user only)
• match: the section to define the criterias to match
  • rules: (list) (OR logic) Falco rules to match. If empty, all rules match.
  • priority: Priority to match. If empty, all priorities match. Syntax is like: >=Critical, <Warning, Debug.
  • tags: (list) (OR logic) Comma separated lists of Tags to match (AND logic). If empty, all tags match.
  • output_fields: (list) (OR logic) Comma separated lists of key:comparison:value for Output fields to match (AND logic). If emtpy, all output fields match.
• actions: the list of actions to sequentially run, they can refer to an action block or defined locally
  • action: (mandatory) name of action to trigger, can refer to an action block
  • description: description of the action (for user only)
  • actionner: name of the actionner to use
  • continue: if true, no more action are applied after this one (each actionner has its own default value).
  • ignore_errors: if true, ignore the errors and avoid to stop at this action.
  • parameters: key:value map of parameters for the action. value can be a string, an array (slice) or a map.
• continue: if true, no more rule are compared after the rule has been triggered (default is true).
• dry_run: if true: the actions are not ran (default: false).
• notifiers: list of notifiers to enabled for the action, in addition with the defaults.

Example

In the below YAML manifest, we can see two different Talon actions - Terminate Pod and Disable outbound connections.

1. The Terminate Pod action has a matching actionner to gracefully terminate a running workload with kubernetes:terminate.
2. The Disable outbound connections action enforces a Kubernetes NetworkPolicy through kubernetes:networkpolicy.

Finally, the two actions are initiated as instant response actions when the matching Falco rule Unexpected outbound connection destination is triggered.

- action: Terminate Pod
  description: terminate the pod if it doesn't belong to a statefulset
  actionner: kubernetes:terminate
  parameters:
    ignoreDaemonsets: false
    ignoreStatefulsets: true

- action: Disable outbound connections
  actionner: kubernetes:networkpolicy
  parameters:
    allow:
      - "192.168.1.0/24"
      - "172.17.0.0/16"
      - "10.0.0.0/32"

- rule: Suspicious outbound connection
  description: Block suspicious outbound connections and terminate the pod
  match:
    rules:
      - Unexpected outbound connection destination
  actions:
    - action: Disable outbound connections
      ignore_errors: true
    - action: Terminate Pod # ref to a re-usable action
      parameters:
        gracePeriods: 2