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Detection rules › Sigma

Okta User Session Start Via An Anonymising Proxy Service

Status
test
Severity
high
Log source
product okta, service okta
Author
kelnage
Source
github.com/SigmaHQ/sigma

Detects when an Okta user session starts where the user is behind an anonymising proxy service.

Known false positives

  • If a user requires an anonymising proxy due to valid justifications.

MITRE ATT&CK coverage

TacticTechniques
Defense Impairment

Telemetry coverage

PlatformRecord / event type
OktaSystem Log event type user.session.start: User logged in to Okta

Rules detecting the same action

These rules filter on the same operation.

Rule body

title: Okta User Session Start Via An Anonymising Proxy Service
id: bde30855-5c53-4c18-ae90-1ff79ebc9578
status: test
description: Detects when an Okta user session starts where the user is behind an anonymising proxy service.
references:
    - https://developer.okta.com/docs/reference/api/system-log/
    - https://sec.okta.com/articles/2023/08/cross-tenant-impersonation-prevention-and-detection
author: kelnage
date: 2023-09-07
modified: 2026-04-27
tags:
    - attack.defense-impairment
    - attack.t1685
logsource:
    product: okta
    service: okta
detection:
    selection:
        eventType: 'user.session.start'
        securityContext.isProxy: 'true'
    condition: selection
falsepositives:
    - If a user requires an anonymising proxy due to valid justifications.
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    eventType: 'user.session.start'
    securityContext.isProxy: 'true'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
eventTypeeq
  • user.session.start
field:"eventType" kind:eq value:"user.session.start"
securityContext.isProxyeq
  • true
field:"securityContext.isProxy" kind:eq value:"true"