Discord CDN Risky File Download ASIM Web Session Schema
Id | 01e8ffff-dc0c-43fe-aa22-d459c4204553 |
Rulename | Discord CDN Risky File Download (ASIM Web Session Schema) |
Description | Identifies callouts to Discord CDN addresses for risky file extensions. This detection will trigger when a callout for a risky file is made to a discord server that has only been seen once in your environment. Unique discord servers are identified using the server ID that is included in the request URL (DiscordServerId in query). Discord CDN has been used in multiple campaigns to download additional payloads. This analytic rule uses ASIM and supports any built-in or custom source that supports the ASIM WebSession schema (ASIM WebSession Schema) |
Severity | Medium |
Tactics | CommandAndControl |
Techniques | T1071.001 |
Required data connectors | SquidProxy Zscaler |
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/ASimWebSession/DiscordCDNRiskyFileDownload_ASim.yaml |
Version | 1.1.4 |
Arm template | 01e8ffff-dc0c-43fe-aa22-d459c4204553.json |
let discord=dynamic(["cdn.discordapp.com", "media.discordapp.com"]);
_Im_WebSession(url_has_any=discord, eventresult='Success')
| where Url has "attachments"
| extend DiscordServerId = extract(@"\/attachments\/([0-9]+)\/", 1, Url)
| summarize dcount(Url), make_set(SrcUsername), make_set(SrcIpAddr), make_set(Url), min(TimeGenerated), max(TimeGenerated), make_set(EventResult) by DiscordServerId
| mv-expand set_SrcUsername to typeof(string), set_Url to typeof(string), set_EventResult to typeof(string), set_SrcIpAddr to typeof(string)
| summarize by DiscordServerId, dcount_Url, set_SrcUsername, min_TimeGenerated, max_TimeGenerated, set_EventResult, set_SrcIpAddr, set_Url
| project StartTime=min_TimeGenerated, EndTime=max_TimeGenerated, Result=set_EventResult, SourceUser=set_SrcUsername, SourceIP=set_SrcIpAddr, RequestURL=set_Url
| where RequestURL has_any (".bin",".exe",".dll",".bin",".msi")
| extend AccountName = tostring(split(SourceUser, "@")[0]), AccountUPNSuffix = tostring(split(SourceUser, "@")[1])
relevantTechniques:
- T1071.001
queryPeriod: 1d
tactics:
- CommandAndControl
requiredDataConnectors:
- dataTypes:
- SquidProxy_CL
connectorId: SquidProxy
- dataTypes:
- CommonSecurityLog
connectorId: Zscaler
triggerThreshold: 0
entityMappings:
- fieldMappings:
- identifier: FullName
columnName: SourceUser
- identifier: Name
columnName: AccountName
- identifier: UPNSuffix
columnName: AccountUPNSuffix
entityType: Account
- fieldMappings:
- identifier: Address
columnName: SourceIP
entityType: IP
- fieldMappings:
- identifier: Url
columnName: RequestURL
entityType: URL
name: Discord CDN Risky File Download (ASIM Web Session Schema)
tags:
- Discord
query: |
let discord=dynamic(["cdn.discordapp.com", "media.discordapp.com"]);
_Im_WebSession(url_has_any=discord, eventresult='Success')
| where Url has "attachments"
| extend DiscordServerId = extract(@"\/attachments\/([0-9]+)\/", 1, Url)
| summarize dcount(Url), make_set(SrcUsername), make_set(SrcIpAddr), make_set(Url), min(TimeGenerated), max(TimeGenerated), make_set(EventResult) by DiscordServerId
| mv-expand set_SrcUsername to typeof(string), set_Url to typeof(string), set_EventResult to typeof(string), set_SrcIpAddr to typeof(string)
| summarize by DiscordServerId, dcount_Url, set_SrcUsername, min_TimeGenerated, max_TimeGenerated, set_EventResult, set_SrcIpAddr, set_Url
| project StartTime=min_TimeGenerated, EndTime=max_TimeGenerated, Result=set_EventResult, SourceUser=set_SrcUsername, SourceIP=set_SrcIpAddr, RequestURL=set_Url
| where RequestURL has_any (".bin",".exe",".dll",".bin",".msi")
| extend AccountName = tostring(split(SourceUser, "@")[0]), AccountUPNSuffix = tostring(split(SourceUser, "@")[1])
queryFrequency: 1d
id: 01e8ffff-dc0c-43fe-aa22-d459c4204553
severity: Medium
description: |
'Identifies callouts to Discord CDN addresses for risky file extensions. This detection will trigger when a callout for a risky file is made to a discord server that has only been seen once in your environment.
Unique discord servers are identified using the server ID that is included in the request URL (DiscordServerId in query). Discord CDN has been used in multiple campaigns to download additional payloads.
This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM WebSession schema (ASIM WebSession Schema)'
metadata:
source:
kind: Community
categories:
domains:
- Security - Threat Protection
support:
tier: Community
author:
name: Microsoft Security Research
version: 1.1.4
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimWebSession/DiscordCDNRiskyFileDownload_ASim.yaml
kind: Scheduled
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": "2023-02-01-preview",
"id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/01e8ffff-dc0c-43fe-aa22-d459c4204553')]",
"kind": "Scheduled",
"name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/01e8ffff-dc0c-43fe-aa22-d459c4204553')]",
"properties": {
"alertRuleTemplateName": "01e8ffff-dc0c-43fe-aa22-d459c4204553",
"customDetails": null,
"description": "'Identifies callouts to Discord CDN addresses for risky file extensions. This detection will trigger when a callout for a risky file is made to a discord server that has only been seen once in your environment. \n Unique discord servers are identified using the server ID that is included in the request URL (DiscordServerId in query). Discord CDN has been used in multiple campaigns to download additional payloads.\n This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM WebSession schema (ASIM WebSession Schema)'\n",
"displayName": "Discord CDN Risky File Download (ASIM Web Session Schema)",
"enabled": true,
"entityMappings": [
{
"entityType": "Account",
"fieldMappings": [
{
"columnName": "SourceUser",
"identifier": "FullName"
},
{
"columnName": "AccountName",
"identifier": "Name"
},
{
"columnName": "AccountUPNSuffix",
"identifier": "UPNSuffix"
}
]
},
{
"entityType": "IP",
"fieldMappings": [
{
"columnName": "SourceIP",
"identifier": "Address"
}
]
},
{
"entityType": "URL",
"fieldMappings": [
{
"columnName": "RequestURL",
"identifier": "Url"
}
]
}
],
"OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimWebSession/DiscordCDNRiskyFileDownload_ASim.yaml",
"query": "let discord=dynamic([\"cdn.discordapp.com\", \"media.discordapp.com\"]);\n _Im_WebSession(url_has_any=discord, eventresult='Success')\n | where Url has \"attachments\"\n | extend DiscordServerId = extract(@\"\\/attachments\\/([0-9]+)\\/\", 1, Url)\n | summarize dcount(Url), make_set(SrcUsername), make_set(SrcIpAddr), make_set(Url), min(TimeGenerated), max(TimeGenerated), make_set(EventResult) by DiscordServerId\n | mv-expand set_SrcUsername to typeof(string), set_Url to typeof(string), set_EventResult to typeof(string), set_SrcIpAddr to typeof(string)\n | summarize by DiscordServerId, dcount_Url, set_SrcUsername, min_TimeGenerated, max_TimeGenerated, set_EventResult, set_SrcIpAddr, set_Url\n | project StartTime=min_TimeGenerated, EndTime=max_TimeGenerated, Result=set_EventResult, SourceUser=set_SrcUsername, SourceIP=set_SrcIpAddr, RequestURL=set_Url\n | where RequestURL has_any (\".bin\",\".exe\",\".dll\",\".bin\",\".msi\")\n | extend AccountName = tostring(split(SourceUser, \"@\")[0]), AccountUPNSuffix = tostring(split(SourceUser, \"@\")[1])\n",
"queryFrequency": "P1D",
"queryPeriod": "P1D",
"severity": "Medium",
"suppressionDuration": "PT1H",
"suppressionEnabled": false,
"tactics": [
"CommandAndControl"
],
"tags": [
"Discord"
],
"techniques": [
"T1071"
],
"templateVersion": "1.1.4",
"triggerOperator": "GreaterThan",
"triggerThreshold": 0
},
"type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
}
]
}