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Detection rules › Sigma

Suspicious Teams Application Related ObjectAcess Event

Status
test
Severity
high
Log source
product windows, service security
Author
@SerkinValery
Source
github.com/SigmaHQ/sigma

Detects an access to authentication tokens and accounts of Microsoft Teams desktop application.

MITRE ATT&CK coverage

TacticTechniques
Credential AccessT1528 Steal Application Access Token

Event coverage

ProviderEventTitle
Security-AuditingEvent ID 4663An attempt was made to access an object.

Rule body yaml

title: Suspicious Teams Application Related ObjectAcess Event
id: 25cde13e-8e20-4c29-b949-4e795b76f16f
status: test
description: Detects an access to authentication tokens and accounts of Microsoft Teams desktop application.
references:
    - https://www.bleepingcomputer.com/news/security/microsoft-teams-stores-auth-tokens-as-cleartext-in-windows-linux-macs/
    - https://www.vectra.ai/blogpost/undermining-microsoft-teams-security-by-mining-tokens
author: '@SerkinValery'
date: 2022-09-16
tags:
    - attack.credential-access
    - attack.t1528
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4663
        ObjectName|contains:
            - '\Microsoft\Teams\Cookies'
            - '\Microsoft\Teams\Local Storage\leveldb'
    filter:
        ProcessName|contains: '\Microsoft\Teams\current\Teams.exe'
    condition: selection and not filter
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection and not filter

Stage 1: selection

selection:
    EventID: 4663
    ObjectName|contains:
        - '\Microsoft\Teams\Cookies'
        - '\Microsoft\Teams\Local Storage\leveldb'

Stage 2: not filter

filter:
    ProcessName|contains: '\Microsoft\Teams\current\Teams.exe'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
ProcessNamematch\Microsoft\Teams\current\Teams.exe

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
ObjectNamematch
  • \Microsoft\Teams\Cookies
  • \Microsoft\Teams\Local Storage\leveldb