Log Architecture & Structural Overview

The Linux /var/log/auth.log & secure PAM Authentication Parser is an essential telemetry stream within the Networking & Security Appliances ecosystem. Parse Linux authentication logs. Audit SSH logins, sudo escalations, invalid user attempts, and brute-force scans.

This schema defines a structure of 12 extracted attributes, including 2 numeric metrics and 10 string dimensions. In production observability architectures, these tokens provide high-cardinality indexing keys for telemetry pipelines before shipping to storage backends such as ClickHouse, Elasticsearch, Amazon S3, or Datadog.

Raw Telemetry Ingestion Profile

A typical raw event line for linux-auth-secure averages 100 bytes across 12 tokens. Modern collectors such as Fluent Bit and Vector require zero-backtracking regular expressions to avoid CPU spikes during traffic surges.

Extracted Field Schema & Data Types

The transpiled Grok pattern extracts the following schema fields from each raw event line. Data collectors cast these values according to the typed mappings below.

Field Name	Inferred Type	Description & Collector Semantics
month	string	Month name abbreviation.
day	string	Day of month.
time	string	Log timestamp (HH:MM:SS).
hostname	string	Host machine name.
program	string	Daemon name (sshd, sudo, su).
pid	integer	Process ID.
auth_result	string	Authentication verdict (Accepted or Failed).
auth_method	string	Authentication method (publickey, password, keyboard-interactive).
user	string	Target username attempting login.
client_ip	string	Source IP address of client.
port	integer	Source client port.
protocol	string	SSH protocol version (ssh2).

Common Regex Traps & Production Edge Cases

Engineers frequently encounter ingestion failures or pipeline drops due to subtle variations in real-world event logs. Watch out for these verified pitfalls:

1On RedHat/CentOS/Rocky Linux, authentication logs are stored in /var/log/secure; on Debian/Ubuntu, in /var/log/auth.log.

2The phrase 'invalid user' appears only when the requested username does not exist on the system.

Production Collector Setup & Configurations

Pre-configured parser definitions ready to be dropped into your infrastructure repository.

Fluent Bit (parsers.conf)

Format: regex

# ==============================================================================
# Fluent Bit Parser Configuration (parsers.conf)
# ==============================================================================
[PARSER]
    Name        logpipeline_parser
    Format      regex
    Regex       ^(?<month>\b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\b)\s+(?<day>(?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9])) (?<time>(?:(?:(?:2[0123]|[01]?[0-9])):(?:(?:[0-5][0-9]))(?::(?:(?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?))))) (?<hostname>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b)) (?<program>\b\w+\b)(?:\[(?<pid>(?:[+-]?(?:[0-9]+)))\])?: (?<auth_result>\b\w+\b) (?<auth_method>\b\w+\b) for (?:invalid user )?(?<user>(?:[a-zA-Z0-9._-]+)) from (?<client_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))) port (?<port>(?:[+-]?(?:[0-9]+))) (?<protocol>\b\w+\b)$
    Time_Key    time
    Time_Format %Y-%m-%dT%H:%M:%S%z
    Types       pid:integer port:integer

# ==============================================================================
# Fluent Bit Pipeline Filter (fluent-bit.conf)
# ==============================================================================
[FILTER]
    Name         parser
    Match        *
    Key_Name     log
    Parser       logpipeline_parser
    Reserve_Data On

Vector.dev (Remap VRL)

parse_regex!

# ==============================================================================
# Vector.dev Remap Language (VRL) Transform
# Use inside a 'remap' transform in vector.yaml
# ==============================================================================
.parsed, err = parse_regex(.message, r'^(?<month>\b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\b)\s+(?<day>(?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9])) (?<time>(?:(?:(?:2[0123]|[01]?[0-9])):(?:(?:[0-5][0-9]))(?::(?:(?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?))))) (?<hostname>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b)) (?<program>\b\w+\b)(?:\[(?<pid>(?:[+-]?(?:[0-9]+)))\])?: (?<auth_result>\b\w+\b) (?<auth_method>\b\w+\b) for (?:invalid user )?(?<user>(?:[a-zA-Z0-9._-]+)) from (?<client_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))) port (?<port>(?:[+-]?(?:[0-9]+))) (?<protocol>\b\w+\b)$')

if err == null {
    . = merge(., .parsed)
    del(.parsed)

    # Type coercions
    .pid = to_int!(.pid)
    .port = to_int!(.port)

} else {
    log("LogPipeline parsing warning: " + err, level: "warn")
}

# ==============================================================================
# vector.yaml Pipeline Component
# ==============================================================================
transforms:
  parse_logs:
    type: remap
    inputs: ["source_logs"]
    source: |
      .parsed, err = parse_regex(.message, r'^(?<month>\b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\b)\s+(?<day>(?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9])) (?<time>(?:(?:(?:2[0123]|[01]?[0-9])):(?:(?:[0-5][0-9]))(?::(?:(?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?))))) (?<hostname>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b)) (?<program>\b\w+\b)(?:\[(?<pid>(?:[+-]?(?:[0-9]+)))\])?: (?<auth_result>\b\w+\b) (?<auth_method>\b\w+\b) for (?:invalid user )?(?<user>(?:[a-zA-Z0-9._-]+)) from (?<client_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))) port (?<port>(?:[+-]?(?:[0-9]+))) (?<protocol>\b\w+\b)$')
      if err == null {
        . = merge(., .parsed)
        del(.parsed)
      }

Datadog Log Pipeline Grok Parser

match_rules

# ==============================================================================
# Datadog Log Processing Pipeline Grok Parser
# Navigate to: Logs -> Configuration -> Pipelines -> Add Processor -> Grok Parser
# ==============================================================================

# Match Rule:
rule %{MONTH:month}\s+%{MONTHDAY:day} %{TIME:time} %{HOSTNAME:hostname} %{WORD:program}(?:\[%{INT:pid}\])?: %{WORD:auth_result} %{WORD:auth_method} for (?:invalid user )?%{USER:user} from %{IP:client_ip} port %{INT:port} %{WORD:protocol}

# Complete Datadog Pipeline Processor JSON:
{
  "type": "grok-parser",
  "name": "LogPipeline Grok Parser",
  "is_enabled": true,
  "source": "message",
  "samples": [],
  "grok": {
    "match_rules": "rule %{MONTH:month}\\s+%{MONTHDAY:day} %{TIME:time} %{HOSTNAME:hostname} %{WORD:program}(?:\\[%{INT:pid}\\])?: %{WORD:auth_result} %{WORD:auth_method} for (?:invalid user )?%{USER:user} from %{IP:client_ip} port %{INT:port} %{WORD:protocol}",
    "support_rules": ""
  }
}

# Target Fields Created:
# month (string), day (string), time (string), hostname (string), program (string), pid (integer), auth_result (string), auth_method (string), user (string), client_ip (string), port (integer), protocol (string)

OpenTelemetry Collector (transform processor)

regex_parser

# ==============================================================================
# OpenTelemetry Collector Configuration (otel-collector-config.yaml)
# Option 1: Filelog Receiver with regex_parser Operator
# ==============================================================================
receivers:
  filelog:
    include: [ /var/log/**/*.log ]
    start_at: beginning
    operators:
      - type: regex_parser
        id: logpipeline_regex_parser
        regex: '^(?<month>\b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\b)\s+(?<day>(?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9])) (?<time>(?:(?:(?:2[0123]|[01]?[0-9])):(?:(?:[0-5][0-9]))(?::(?:(?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?))))) (?<hostname>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b)) (?<program>\b\w+\b)(?:\[(?<pid>(?:[+-]?(?:[0-9]+)))\])?: (?<auth_result>\b\w+\b) (?<auth_method>\b\w+\b) for (?:invalid user )?(?<user>(?:[a-zA-Z0-9._-]+)) from (?<client_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))) port (?<port>(?:[+-]?(?:[0-9]+))) (?<protocol>\b\w+\b)$'
        timestamp:
          parse_from: attributes.time
          layout: '%Y-%m-%dT%H:%M:%S%z'

# ==============================================================================
# Option 2: Transform Processor (OTel Transformation Language - OTTL)
# ==============================================================================
processors:
  transform:
    error_mode: ignore
    log_statements:
      - context: log
        statements:
          - merge_maps(attributes, extract_patterns(body, "^(?<month>\\b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\\b)\\s+(?<day>(?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9])) (?<time>(?:(?:(?:2[0123]|[01]?[0-9])):(?:(?:[0-5][0-9]))(?::(?:(?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?))))) (?<hostname>\\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\\.?|\\b)) (?<program>\\b\\w+\\b)(?:\\[(?<pid>(?:[+-]?(?:[0-9]+)))\\])?: (?<auth_result>\\b\\w+\\b) (?<auth_method>\\b\\w+\\b) for (?:invalid user )?(?<user>(?:[a-zA-Z0-9._-]+)) from (?<client_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))) port (?<port>(?:[+-]?(?:[0-9]+))) (?<protocol>\\b\\w+\\b)$"), "insert")

service:
  pipelines:
    logs:
      receivers: [filelog]
      processors: [transform]
      exporters: [otlp]

Logstash Filter Configuration

filter.grok

# ==============================================================================
# Logstash Pipeline Configuration (/etc/logstash/conf.d/logpipeline.conf)
# ==============================================================================
filter {
  grok {
    match => { "message" => "%{MONTH:month}\s+%{MONTHDAY:day} %{TIME:time} %{HOSTNAME:hostname} %{WORD:program}(?:\[%{INT:pid:integer}\])?: %{WORD:auth_result} %{WORD:auth_method} for (?:invalid user )?%{USER:user} from %{IP:client_ip} port %{INT:port:integer} %{WORD:protocol}" }
    tag_on_failure => [ "_grokparsefailure" ]
  }

  date {
    match => [ "time", "ISO8601", "dd/MMM/yyyy:HH:mm:ss Z" ]
    target => "@timestamp"
    remove_field => [ "time" ]
  }
}