Silk Typhoon Suspicious File Downloads

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 HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)

severity: Medium
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/http_proxy_oab_CL/SilkTyphoonSuspiciousFileDownloads.yaml
queryPeriod: 1d
triggerThreshold: 0
queryFrequency: 1d
requiredDataConnectors: []
id: 03e04c97-8cae-48b3-9d2f-4ab262e4ffff
metadata:
  source:
    kind: Community
  categories:
    domains:
    - Security - 0-day Vulnerability
  author:
    name: Microsoft Security Research
  support:
    tier: Community
name: 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/'
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 HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
tactics:
- InitialAccess
version: 1.0.3
kind: Scheduled
relevantTechniques:
- T1190
entityMappings:
- entityType: Host
  fieldMappings:
  - identifier: FullName
    columnName: Computer
  - identifier: HostName
    columnName: HostName
  - identifier: DnsDomain
    columnName: HostNameDomain
triggerOperator: gt

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-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": "Computer",
                "identifier": "FullName"
              },
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "HostNameDomain",
                "identifier": "DnsDomain"
              }
            ]
          }
        ],
        "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 HostName = tostring(split(Computer, \".\")[0]), DomainIndex = toint(indexof(Computer, '.'))\n| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Medium",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1190"
        ],
        "templateVersion": "1.0.3",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}