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Detection rules › Kusto

Cisco SEG - Suspicious link

Status
available
Severity
high
Time window
15m
Source
github.com/Azure/Azure-Sentinel

'Detects mails with suspicious links.'

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1566 Phishing

Rule body kusto

id: 506291dd-8050-4c98-a92f-58e376080a0a
name: Cisco SEG - Suspicious link
description: |
  'Detects mails with suspicious links.'
severity: High
status: Available
requiredDataConnectors:
  - connectorId: CefAma
    dataTypes:
      - CommonSecurityLog
queryFrequency: 15m
queryPeriod: 15m
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
query: |
  let bl_cat = dynamic(['Adult', 'Hacking', 'Cheating and Plagiarism', 'Child Abuse Content', 'Dating', 'Illegal Activities', 'Pornography']);
  CiscoSEGEvent
  | where NetworkDirection =~ 'Incoming'
  | where tostring(AdditionalFields) has 'ESAURLDetails'
  | extend link_cat = extract(@"'Category': '(.*?)'", 1, tostring(AdditionalFields))
  | where link_cat in~ (bl_cat)
  | extend AccountCustomEntity = DstUserName
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: AccountCustomEntity
version: 1.0.3
kind: Scheduled

Stages and Predicates

Parameters

let bl_cat = dynamic(['Adult', 'Hacking', 'Cheating and Plagiarism', 'Child Abuse Content', 'Dating', 'Illegal Activities', 'Pornography']);

Stage 1: source

CiscoSEGEvent

Stage 2: where

| where NetworkDirection =~ 'Incoming'

Stage 3: where

| where tostring(AdditionalFields) has 'ESAURLDetails'

Stage 4: extend

| extend link_cat = extract(@"'Category': '(.*?)'", 1, tostring(AdditionalFields))

Stage 5: where

| where link_cat in~ (bl_cat)

Stage 6: extend

| extend AccountCustomEntity = DstUserName

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
AdditionalFieldsmatch
  • ESAURLDetails transforms: tostring, term
NetworkDirectioneq
  • Incoming
link_catin
  • Adult
  • Cheating and Plagiarism
  • Child Abuse Content
  • Dating
  • Hacking
  • Illegal Activities
  • Pornography

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

FieldSource
link_catextend
AccountCustomEntityextend