Home
Reference Guides
Reference material for alerts and incidents, discovery and Smart Polling strategies, and Federal Information Processing Standards.
Alerts and Incidents
Reference guide for alerts and incidents.
Alerts
A description of alerts in the Nozomi Networks software.
Custom checks
These are checks set in place by the user. Typically the nature of an event related to a custom check cannot generally be referred to a problem per se, if not contextualized to the specific network and installation.
NET:TCP-SYN
TCP SYN

Reference Guides
Reference material for alerts and incidents, discovery and Smart Polling strategies, and Federal Information Processing Standards.
- Alerts and Incidents
  Reference guide for alerts and incidents.
  - Alerts
    A description of alerts in the Nozomi Networks software.
    - Built-in checks
      Built-in checks are based on specific signatures or hard-coded logics with reference to: known ICS threats (by signatures provided by Threat Intelligence), known malicious operations, system weaknesses, or protocol-compliant operations that can impact the network/ICS functionality. They might also leverage the Learning process to be more accurate.
    - Custom checks
      These are checks set in place by the user. Typically the nature of an event related to a custom check cannot generally be referred to a problem per se, if not contextualized to the specific network and installation.
      - ASRT:FAILED
        Assertion failed
      - GENERIC:EVENT
        Generic Event
      - NET:INACTIVE-PROTOCOL
        Inactive protocol
      - NET:LINK-RECONNECTION
        Link reconnection
      - NET:TCP-SYN
        TCP SYN
      - PROC:CRITICAL-STATE-OFF
        Critical state off
      - PROC:CRITICAL-STATE-ON
        Critical state on
      - PROC:INVALID-VARIABLE-QUALITY
        Invalid variable quality
      - PROC:NOT-ALLOWED-INVALID-VARIABLE
        Not allowed variable quality
      - PROC:STALE-VARIABLE
        Stale variable
    - Protocol validations
      An undesired protocol behavior has been detected. This can refer to a wrong single message, to a correct single message not supposed to be transmitted or transmitted at the wrong time (state machines violation) or to a malicious message sequence. Protocol specific error messages indicating misconfigurations also trigger alerts that fall into this category.
    - Learned behavior (virtual image)
      Virtual image represents a set of information by which Guardian represents the monitored network. This includes for example node properties, links, protocols, function codes, variables, variable values. Such information is collected via learning, smart polling, or external contents, such as Asset Intelligence. Alerts in this group represent deviations from expected behaviors, according to the learned or fed information. When an alert of this category is raised, if the related event is not considered a malicious attack or an anomaly, it can be learned.
  - Incidents
    Incidents are a set of alerts that are related to each other. You can use them to streamline alerts analysis. The user interface (UI) lets you group alerts into incidents. You can toggle the view between Alerts or Incidents.
- Discovery
  Reference guide for discovery strategies.
- Smart Polling
  Reference guide for Smart Polling strategies.
- Federal Information Processing Standards
  Reference guide for Federal Information Processing Standards.
- N2OS Configuration Reference
  Reference guide for the current N2OS configuration settings (versioned publication).

NET:TCP-SYN

TCP SYN

Type ID

NET:TCP-SYN

Security profile

Alerts of this type are visible in the following security profiles:

LOW
MEDIUM
HIGH
PARANOID

Risk

The base risk for this alert is 3.

Cause

A connection attempt (TCP SYN) has been detected on a link.

Solution

Investigate on the entity that has attempted to connect.

Product versions

Guardian 18.0.0

Trace

Alerts of this type are expected to generate traces.

Deduplication key

Attribute SOURCE_NODE_ID
Attribute DESTINATION_NODE_ID
Attribute SOURCE_MAC
Attribute DESTINATION_MAC
Attribute TYPE_ID
Attribute TRIGGER_ID