Silk Typhoon Suspicious File Downloads

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Id	03e04c97-8cae-48b3-9d2f-4ab262e4ffff
Rulename	Silk Typhoon Suspicious File Downloads.
Description	This query looks for messages related to file downloads of suspicious file types. This query uses the Exchange HttpProxy AOBGeneratorLog, you will need to onboard this log as a custom log under the table http_proxy_oab_CL before using this query. Reference: https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
Severity	Medium
Tactics	InitialAccess
Techniques	T1190
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/http_proxy_oab_CL/SilkTyphoonSuspiciousFileDownloads.yaml
Version	1.0.2
Arm template	03e04c97-8cae-48b3-9d2f-4ab262e4ffff.json

KQL

let scriptExtensions = dynamic([".php", ".jsp", ".js", ".aspx", ".asmx", ".asax", ".cfm", ".shtml"]);
http_proxy_oab_CL
| where RawData contains "Download failed and temporary file"
| extend File = extract("([^\\\\]*)(\\\\[^']*)",2,RawData)
| extend Extension = strcat(".",split(File, ".")[-1])
| extend InteractiveFile = iif(Extension in (scriptExtensions), "Yes", "No")
// Uncomment the following line to alert only on interactive file download type
//| where InteractiveFile =~ "Yes"
| extend timestamp = TimeGenerated, HostCustomEntity = Computer

YAML

id: 03e04c97-8cae-48b3-9d2f-4ab262e4ffff
queryPeriod: 1d
severity: Medium
kind: Scheduled
query: |
  let scriptExtensions = dynamic([".php", ".jsp", ".js", ".aspx", ".asmx", ".asax", ".cfm", ".shtml"]);
  http_proxy_oab_CL
  | where RawData contains "Download failed and temporary file"
  | extend File = extract("([^\\\\]*)(\\\\[^']*)",2,RawData)
  | extend Extension = strcat(".",split(File, ".")[-1])
  | extend InteractiveFile = iif(Extension in (scriptExtensions), "Yes", "No")
  // Uncomment the following line to alert only on interactive file download type
  //| where InteractiveFile =~ "Yes"
  | extend timestamp = TimeGenerated, HostCustomEntity = Computer  
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: HostCustomEntity
  entityType: Host
triggerThreshold: 0
metadata:
  categories:
    domains:
    - Security - 0-day Vulnerability
  author:
    name: petebryan
  source:
    kind: Community
  support:
    tier: Community
description: |
  'This query looks for messages related to file downloads of suspicious file types. This query uses the Exchange HttpProxy AOBGeneratorLog, you will need to onboard this log as a custom log under the table http_proxy_oab_CL before using this query. 
  Reference: https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/'  
name: Silk Typhoon Suspicious File Downloads.
relevantTechniques:
- T1190
queryFrequency: 1d
requiredDataConnectors: []
tactics:
- InitialAccess
triggerOperator: gt
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/http_proxy_oab_CL/SilkTyphoonSuspiciousFileDownloads.yaml
version: 1.0.2

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2023-02-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/03e04c97-8cae-48b3-9d2f-4ab262e4ffff')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/03e04c97-8cae-48b3-9d2f-4ab262e4ffff')]",
      "properties": {
        "alertRuleTemplateName": "03e04c97-8cae-48b3-9d2f-4ab262e4ffff",
        "customDetails": null,
        "description": "'This query looks for messages related to file downloads of suspicious file types. This query uses the Exchange HttpProxy AOBGeneratorLog, you will need to onboard this log as a custom log under the table http_proxy_oab_CL before using this query. \nReference: https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/'\n",
        "displayName": "Silk Typhoon Suspicious File Downloads.",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "HostCustomEntity",
                "identifier": "FullName"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/http_proxy_oab_CL/SilkTyphoonSuspiciousFileDownloads.yaml",
        "query": "let scriptExtensions = dynamic([\".php\", \".jsp\", \".js\", \".aspx\", \".asmx\", \".asax\", \".cfm\", \".shtml\"]);\nhttp_proxy_oab_CL\n| where RawData contains \"Download failed and temporary file\"\n| extend File = extract(\"([^\\\\\\\\]*)(\\\\\\\\[^']*)\",2,RawData)\n| extend Extension = strcat(\".\",split(File, \".\")[-1])\n| extend InteractiveFile = iif(Extension in (scriptExtensions), \"Yes\", \"No\")\n// Uncomment the following line to alert only on interactive file download type\n//| where InteractiveFile =~ \"Yes\"\n| extend timestamp = TimeGenerated, HostCustomEntity = Computer\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Medium",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1190"
        ],
        "templateVersion": "1.0.2",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}