Suspicious link sharing pattern

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Id	1218175f-c534-421c-8070-5dcaabf28067
Rulename	Suspicious link sharing pattern
Description	Alerts in links that have been shared across multiple Zoom chat channels by the same user in a short space if time. Adjust the threshold figure to change the number of channels a message needs to be posted in before an alert is raised.
Severity	Low
Tactics	Reconnaissance
Techniques	T1598
Kind	Scheduled
Query frequency	1d
Query period	1d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ZoomLogs/SupiciousLinkSharing.yaml
Version	1.0.4
Arm template	1218175f-c534-421c-8070-5dcaabf28067.json

KQL

let threshold = 3;
ZoomLogs
| where Event =~ "chat_message.sent"
| extend Channel = tostring(parse_json(ChatEvents).Channel)
| extend Message = tostring(parse_json(ChatEvents).Message)
| where Message matches regex "http(s?):\\/\\/"
| summarize Channels = makeset(Channel), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by Message, User, UserId
| extend ChannelCount = arraylength(Channels)
| where ChannelCount > threshold
| extend AccountName = tostring(split(User, "@")[0]), AccountUPNSuffix = tostring(split(User, "@")[1])

YAML

queryPeriod: 1d
query: |
  let threshold = 3;
  ZoomLogs
  | where Event =~ "chat_message.sent"
  | extend Channel = tostring(parse_json(ChatEvents).Channel)
  | extend Message = tostring(parse_json(ChatEvents).Message)
  | where Message matches regex "http(s?):\\/\\/"
  | summarize Channels = makeset(Channel), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by Message, User, UserId
  | extend ChannelCount = arraylength(Channels)
  | where ChannelCount > threshold
  | extend AccountName = tostring(split(User, "@")[0]), AccountUPNSuffix = tostring(split(User, "@")[1])  
name: Suspicious link sharing pattern
entityMappings:
- fieldMappings:
  - columnName: User
    identifier: FullName
  - columnName: AccountName
    identifier: Name
  - columnName: AccountUPNSuffix
    identifier: UPNSuffix
  entityType: Account
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ZoomLogs/SupiciousLinkSharing.yaml
requiredDataConnectors: []
description: |
  'Alerts in links that have been shared across multiple Zoom chat channels by the same user in a short space if time.
  Adjust the threshold figure to change the number of channels a message needs to be posted in before an alert is raised.'  
kind: Scheduled
version: 1.0.4
metadata:
  author:
    name: Microsoft Security Research
  categories:
    domains:
    - Security - Others
  support:
    tier: Community
  source:
    kind: Community
queryFrequency: 1d
severity: Low
relevantTechniques:
- T1598
triggerOperator: gt
triggerThreshold: 0
tactics:
- Reconnaissance
id: 1218175f-c534-421c-8070-5dcaabf28067

ARM