Suspicious Browser Activity — Sigma Rule

Rule metadata and linked tags

Author: Mark Morowczynski '@markmorow', Gloria Lee, '@gleeiamglo'. Source status: test; severity: high. Source dates: 2023-09-03 / not supplied.

{
  "product": "azure",
  "service": "riskdetection"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 51da4838ed03cec094181ad0b22305b26fe8a155fb454ec11b77661e80f606f2

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Suspicious Browser Activity
id: 944f6adb-7a99-4c69-80c1-b712579e93e6
status: test
description: Indicates anomalous behavior based on suspicious sign-in activity across multiple tenants from different countries in the same browser
references:
    - https://learn.microsoft.com/en-us/entra/id-protection/concept-identity-protection-risks#suspicious-browser
    - https://learn.microsoft.com/en-us/entra/architecture/security-operations-user-accounts#unusual-sign-ins
author: Mark Morowczynski '@markmorow', Gloria Lee, '@gleeiamglo'
date: 2023-09-03
tags:
    - attack.stealth
    - attack.t1078
    - attack.persistence
    - attack.privilege-escalation
    - attack.initial-access
logsource:
    product: azure
    service: riskdetection
detection:
    selection:
        riskEventType: 'suspiciousBrowser'
    condition: selection
falsepositives:
    - We recommend investigating the sessions flagged by this detection in the context of other sign-ins from the user.
level: high

Original YAML and metadata in JSON

False positives

• We recommend investigating the sessions flagged by this detection in the context of other sign-ins from the user.

Source references

• https://learn.microsoft.com/en-us/entra/id-protection/concept-identity-protection-risks#suspicious-browser
• https://learn.microsoft.com/en-us/entra/architecture/security-operations-user-accounts#unusual-sign-ins