Rare client observed with high reverse DNS lookup count - Static threshold based ASIM DNS Solution
Id | 77b7c820-5f60-4779-8bdb-f06e21add5f1 |
Rulename | Rare client observed with high reverse DNS lookup count - Static threshold based (ASIM DNS Solution) |
Description | This rule identifies clients with high reverse DNS counts, which could be carrying out reconnaissance or discovery activity. This helps in detecting the possible initial phases of an attack, like discovery and reconnaissance. It utilizes ASIM normalization and is applied to any source that supports the ASIM DNS schema. |
Severity | Medium |
Tactics | Reconnaissance |
Techniques | T1590 |
Kind | Scheduled |
Query frequency | 1d |
Query period | 10d |
Trigger threshold | 0 |
Trigger operator | gt |
Source Uri | https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/RareClientObservedWithHighReverseDNSLookupCountStaticThresholdBased.yaml |
Version | 1.0.2 |
Arm template | 77b7c820-5f60-4779-8bdb-f06e21add5f1.json |
let threshold = 10;
let stime = 10d;
let etime = 1d;
let SearchDomain = dynamic(["in-addr.arpa"]);
_Im_Dns(starttime=ago(etime), domain_has_any=SearchDomain)
| summarize
StartTimeUtc = min(TimeGenerated),
EndTimeUtc = max(TimeGenerated),
DNSQueryCount=dcount(DnsQuery)
by SrcIpAddr
| where DNSQueryCount > threshold
| project StartTimeUtc, EndTimeUtc, SrcIpAddr, DNSQueryCount
| join kind=leftanti (_Im_Dns(starttime=ago(stime), endtime=ago(etime), domain_has_any=SearchDomain)
| summarize DNSQueryCount=dcount(DnsQuery) by SrcIpAddr, bin(TimeGenerated, 1d)
| where DNSQueryCount > threshold
| project SrcIpAddr, DNSQueryCount
)
on SrcIpAddr
| join kind=inner (_Im_Dns(starttime=ago(etime), domain_has_any=SearchDomain)
| summarize DNSQueries=make_set(DnsQuery, 1000) by SrcIpAddr)
on SrcIpAddr
| extend DNSQuerythreshold = threshold
| project-away SrcIpAddr1
relevantTechniques:
- T1590
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/RareClientObservedWithHighReverseDNSLookupCountStaticThresholdBased.yaml
triggerOperator: gt
kind: Scheduled
entityMappings:
- fieldMappings:
- columnName: SrcIpAddr
identifier: Address
entityType: IP
eventGroupingSettings:
aggregationKind: AlertPerResult
requiredDataConnectors: []
queryPeriod: 10d
query: |
let threshold = 10;
let stime = 10d;
let etime = 1d;
let SearchDomain = dynamic(["in-addr.arpa"]);
_Im_Dns(starttime=ago(etime), domain_has_any=SearchDomain)
| summarize
StartTimeUtc = min(TimeGenerated),
EndTimeUtc = max(TimeGenerated),
DNSQueryCount=dcount(DnsQuery)
by SrcIpAddr
| where DNSQueryCount > threshold
| project StartTimeUtc, EndTimeUtc, SrcIpAddr, DNSQueryCount
| join kind=leftanti (_Im_Dns(starttime=ago(stime), endtime=ago(etime), domain_has_any=SearchDomain)
| summarize DNSQueryCount=dcount(DnsQuery) by SrcIpAddr, bin(TimeGenerated, 1d)
| where DNSQueryCount > threshold
| project SrcIpAddr, DNSQueryCount
)
on SrcIpAddr
| join kind=inner (_Im_Dns(starttime=ago(etime), domain_has_any=SearchDomain)
| summarize DNSQueries=make_set(DnsQuery, 1000) by SrcIpAddr)
on SrcIpAddr
| extend DNSQuerythreshold = threshold
| project-away SrcIpAddr1
alertDetailsOverride:
alertDisplayNameFormat: "[Static threshold] Rare client has been observed as making high reverse DNS lookup count - client IP: '{{SrcIpAddr}}'"
alertDescriptionFormat: |-
Client identified as making high reverse DNS counts which could be carrying out reconnaissance or discovery activity.
Reverse DNS lookup threshold is: '{{DNSQuerythreshold}}'
Current reverse DNS lookup count from this client is : '{{DNSQueryCount}}'
DNS queries requested by this client inlcude: '{{DNSQueries}}'
version: 1.0.2
customDetails:
DNSQuerythreshold: DNSQuerythreshold
DNSQueries: DNSQueries
DNSQueryCount: DNSQueryCount
description: |
'This rule identifies clients with high reverse DNS counts, which could be carrying out reconnaissance or discovery activity. This helps in detecting the possible initial phases of an attack, like discovery and reconnaissance. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
tactics:
- Reconnaissance
severity: Medium
name: Rare client observed with high reverse DNS lookup count - Static threshold based (ASIM DNS Solution)
tags:
- SchemaVersion: 0.1.6
Schema: ASimDns
queryFrequency: 1d
triggerThreshold: 0
status: Available
id: 77b7c820-5f60-4779-8bdb-f06e21add5f1
{
"$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/77b7c820-5f60-4779-8bdb-f06e21add5f1')]",
"kind": "Scheduled",
"name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/77b7c820-5f60-4779-8bdb-f06e21add5f1')]",
"properties": {
"alertDetailsOverride": {
"alertDescriptionFormat": "Client identified as making high reverse DNS counts which could be carrying out reconnaissance or discovery activity.\n\nReverse DNS lookup threshold is: '{{DNSQuerythreshold}}'\n\nCurrent reverse DNS lookup count from this client is : '{{DNSQueryCount}}'\n\nDNS queries requested by this client inlcude: '{{DNSQueries}}'",
"alertDisplayNameFormat": "[Static threshold] Rare client has been observed as making high reverse DNS lookup count - client IP: '{{SrcIpAddr}}'"
},
"alertRuleTemplateName": "77b7c820-5f60-4779-8bdb-f06e21add5f1",
"customDetails": {
"DNSQueries": "DNSQueries",
"DNSQueryCount": "DNSQueryCount",
"DNSQuerythreshold": "DNSQuerythreshold"
},
"description": "'This rule identifies clients with high reverse DNS counts, which could be carrying out reconnaissance or discovery activity. This helps in detecting the possible initial phases of an attack, like discovery and reconnaissance. It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'\n",
"displayName": "Rare client observed with high reverse DNS lookup count - Static threshold based (ASIM DNS Solution)",
"enabled": true,
"entityMappings": [
{
"entityType": "IP",
"fieldMappings": [
{
"columnName": "SrcIpAddr",
"identifier": "Address"
}
]
}
],
"eventGroupingSettings": {
"aggregationKind": "AlertPerResult"
},
"OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/DNS Essentials/Analytic Rules/RareClientObservedWithHighReverseDNSLookupCountStaticThresholdBased.yaml",
"query": "let threshold = 10;\nlet stime = 10d;\nlet etime = 1d;\nlet SearchDomain = dynamic([\"in-addr.arpa\"]);\n_Im_Dns(starttime=ago(etime), domain_has_any=SearchDomain)\n| summarize\n StartTimeUtc = min(TimeGenerated),\n EndTimeUtc = max(TimeGenerated),\n DNSQueryCount=dcount(DnsQuery)\n by SrcIpAddr\n| where DNSQueryCount > threshold\n| project StartTimeUtc, EndTimeUtc, SrcIpAddr, DNSQueryCount \n| join kind=leftanti (_Im_Dns(starttime=ago(stime), endtime=ago(etime), domain_has_any=SearchDomain)\n | summarize DNSQueryCount=dcount(DnsQuery) by SrcIpAddr, bin(TimeGenerated, 1d)\n | where DNSQueryCount > threshold\n | project SrcIpAddr, DNSQueryCount\n )\n on SrcIpAddr\n| join kind=inner (_Im_Dns(starttime=ago(etime), domain_has_any=SearchDomain)\n | summarize DNSQueries=make_set(DnsQuery, 1000) by SrcIpAddr)\n on SrcIpAddr\n| extend DNSQuerythreshold = threshold\n| project-away SrcIpAddr1\n",
"queryFrequency": "P1D",
"queryPeriod": "P10D",
"severity": "Medium",
"status": "Available",
"suppressionDuration": "PT1H",
"suppressionEnabled": false,
"tactics": [
"Reconnaissance"
],
"tags": [
{
"Schema": "ASimDns",
"SchemaVersion": "0.1.6"
}
],
"techniques": [
"T1590"
],
"templateVersion": "1.0.2",
"triggerOperator": "GreaterThan",
"triggerThreshold": 0
},
"type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
}
]
}