Passive Monitoring

NetEye’s passive monitoring abilities count on Tornado, a Complex Event Processor that receives reports of events from data sources such as monitoring, email, and telegram, matches them against pre-configured rules, and executes the actions associated with those rules, which can include sending notifications, logging to files, and annotating events in a time series graphing system.

Tornado is a high performance, scalable application, and is intended to handle millions of events each second on standard server hardware. This

Fig. 17 Tornado architecture

Tornado Architecture

Tornado is structured as a library, with three example binaries included that show how it can be used. The three main components of the Tornado architecture are:

• The Tornado Collector(s), or just Collector(s)

• The Tornado Engine, or Engine

• The Tornado Executor(s), or Executor(s)*

The term Tornado refers to the whole project or to a deployed system that includes all three components.

Along with the main components, the following concepts are fundamental to the Tornado architecture:

• A Datasource: A system that sends External Events* to Tornado, or a system to which Tornado subscribes to receive External Events.

• An External Event: An input received from a datasource. Its format depends on its source. An example of this is events from rsyslog.

• A Tornado (or Internal) Event: The Tornado-specific Event format.

• A Rule: A group of conditions that an Internal Event must match to trigger a set of Actions.

• An Action: An operation performed by Tornado, usually on an external system. For example, writing to Elastic Search or setting a state in a monitoring system.

Architecturally, Tornado is organized as a processing pipeline, where input events move from collectors to the engine, to executors, without branching or returning.

When the system receives an External Event, it first arrives at a Collector where it is converted into a Tornado Event. Then it is forwarded to the Tornado Engine where it is matched against user-defined, composable Rules. Finally, generated Actions are dispatched to the Executors.

The Tornado pipeline:

Datasources (e.g. rsyslog)
  |
  | External Events
  |
  \-> Tornado Collectors
        |
        | Tornado (or Internal) Events
        |
        \-> Tornado Engine (matches based on Rules)
              |
              | Actions
              |
              \-> Tornado Executors (execute the Actions)

Collectors

The purpose of a Collector is to receive and convert external events into the internal Tornado Event structure, and forward them to the Tornado Engine.

Collectors are Datasource-specific. For each datasource, there must be at least one collector that knows how to manipulate the datasource’s Events and generate Tornado Events.

Out of the box, Tornado provides a number of Collectors for handling inputs from snmptrapd, rsyslog, JSON from Nats channels and generic Webhooks.

Because all Collectors are defined with a simple format, Collectors for new event types can easily be added or extended from existing types for:

• Monitoring events

• Email messages

• Telegram

• DNS

• Cloud monitoring (AWS, Azure, Cisco/Meraki, etc.)

• Netflow

• Elastic Stack

• SMS

• Operating system and authorization events

Engine

The Engine is the second step of the pipeline. It receives and processes the events produced by the Collectors. The outcome of this step is fully defined by a processing tree composed of Filters and Rule Sets.

A Filter is a processing node that defines an access condition on the children nodes.

A Rule Set is a node that contains an ordered set of Rules, where each Rule determines:

• The conditions a Tornado Event has to respect to match it

• The actions to be executed in case of a match

The processing tree is parsed at startup from a configuration folder where the node definitions are stored in JSON format.

When an event matches one or more Rules, the Engine produces a set of Actions and forwards them to one or more Executors.

Executors

The Executors are the last element in the Tornado pipeline. They receive the Actions produced from the Engine and trigger the associated executable instructions.

An Action can be any command, process or operation. For example it can include: * Forwarding the events to a monitoring system * Logging events locally (e.g., as processed, discarded or matched) or remotely * Archiving events using software such as the Elastic Stack * Invoking a custom shell script

A single Executor usually takes care of a single Action type.

Tornado Crates Documentation Links

Tornado’s crate docs are produced according to the Rust documentation standards. The shortcuts below, organized thematically, will take you to the documentation for each module.

Common Traits and Code

The Common API page describes the API and defines the Event and Action structures.

• tornado_common_api

The Logger page describes how Tornado logs its own actions.

• tornado_common_logger

Collectors

This crate describes the commonalities of all Collector types.

• tornado_collector_common

Describes a collector that receives a MIME email message and generates an Event.

• tornado_collector_email

This page illustrates the Collector for JSON events using the JMESPath JSON query language.

• tornado_collector_jmespath

Presents the standard JSON collector that deserializes an unstructured JSON string into an Event.

• tornado_collector_json

Engine

The Matcher page describes the structure of the rules used in matching.

• tornado_engine_matcher

Executors

This crate describes the commonalities of all Executor types.

• tornado_executor_common

This page describes how the Archive executor writes to log files on locally mounted file systems, with a focus on configuration.

• tornado_executor_archive

The Icinga2 executor forwards Tornado Actions to the Icinga2 API.

• tornado_executor_icinga2

The Logger executor simply outputs the whole Action body to the standard log at the info level.

• tornado_executor_logger

The Executor Script page defines how to configure Actions that launch shell scripts.

• tornado_executor_script

Network

This page contains high level traits not bound to any specific network technology.

• tornado_network_common

Describes tests that dispatch Events and Actions on a single process without actually making network calls.

• tornado_network_simple

Executables

Describes the structure of the Tornado binary executable, and the structure and configuration of many of its components.

• tornado_engine

An executable that processes incoming emails and generates Tornado Events.

• tornado_email_collector

An executable that subscribes to Icinga2 Event Streams API and generates Tornado Events.

• tornado_icinga2_collector

An executable that subscribes to Nats channels and generates Tornado Events.

• tornado_nats_json_collector

The description of a binary executable that generates Tornado Events from rsyslog inputs.

• tornado_rsyslog_collector

A Perl trap handler for Net-SNMP’s to subscribe to snmptrapd events.

• tornado_snmptrapd_collector

A standalone HTTP server binary executable that listens for REST calls from a generic Webhook.

• tornado_webhook_collector

Tornado License

Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option. All files in the project carrying such notice may not be copied, modified, or distributed except according to those terms.