Process executed from binary hidden in Base64 encoded file
Id | d6190dde-8fd2-456a-ac5b-0a32400b0464 |
Rulename | Process executed from binary hidden in Base64 encoded file |
Description | Encoding malicious software is a technique used to obfuscate files from detection. The first CommandLine component is looking for Python decoding base64. The second CommandLine component is looking for Bash/sh command line base64 decoding. The third one is looking for Ruby decoding base64. |
Severity | Medium |
Tactics | Execution DefenseEvasion |
Techniques | T1059 T1027 T1140 |
Required data connectors | SecurityEvents WindowsForwardedEvents WindowsSecurityEvents |
Kind | Scheduled |
Query frequency | 1d |
Query period | 1d |
Trigger threshold | 0 |
Trigger operator | gt |
Source Uri | https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint Threat Protection Essentials/Analytic Rules/execute_base64_decodedpayload.yaml |
Version | 1.1.3 |
Arm template | d6190dde-8fd2-456a-ac5b-0a32400b0464.json |
let ProcessCreationEvents=(union isfuzzy=true
(SecurityEvent
| where EventID==4688
| where isnotempty(CommandLine)
| project TimeGenerated, Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName, FileName = Process, CommandLine, ParentProcessName
),
(WindowsEvent
| where EventID==4688
| where EventData has_any (".decode('base64')", "base64 --decode", ".decode64(" )
| extend CommandLine = tostring(EventData.CommandLine)
| where isnotempty(CommandLine)
| extend SubjectUserName = tostring(EventData.SubjectUserName)
| extend SubjectDomainName = tostring(EventData.SubjectDomainName)
| extend NewProcessName = tostring(EventData.NewProcessName)
| extend FileName=tostring(split(NewProcessName, '\\')[-1])
| extend ParentProcessName = tostring(EventData.ParentProcessName)
| project TimeGenerated, Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName, CommandLine, ParentProcessName
));
ProcessCreationEvents
| where CommandLine contains ".decode('base64')"
or CommandLine contains "base64 --decode"
or CommandLine contains ".decode64("
| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), CountToday = count() by Computer, Account, AccountDomain, FileName, CommandLine, ParentProcessName
| extend HostName = iif(Computer has '.',substring(Computer,0,indexof(Computer,'.')),Computer) , DnsDomain = iif(Computer has '.',substring(Computer,indexof(Computer,'.')+1),'')
queryPeriod: 1d
version: 1.1.3
tactics:
- Execution
- DefenseEvasion
queryFrequency: 1d
id: d6190dde-8fd2-456a-ac5b-0a32400b0464
triggerOperator: gt
requiredDataConnectors:
- dataTypes:
- SecurityEvent
connectorId: SecurityEvents
- dataTypes:
- SecurityEvent
connectorId: WindowsSecurityEvents
- dataTypes:
- SecurityEvents
connectorId: WindowsSecurityEvents
- dataTypes:
- WindowsEvent
connectorId: WindowsForwardedEvents
severity: Medium
entityMappings:
- entityType: Account
fieldMappings:
- columnName: Account
identifier: Name
- entityType: Host
fieldMappings:
- columnName: Computer
identifier: FullName
- columnName: HostName
identifier: HostName
- columnName: DnsDomain
identifier: DnsDomain
triggerThreshold: 0
relevantTechniques:
- T1059
- T1027
- T1140
query: |
let ProcessCreationEvents=(union isfuzzy=true
(SecurityEvent
| where EventID==4688
| where isnotempty(CommandLine)
| project TimeGenerated, Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName, FileName = Process, CommandLine, ParentProcessName
),
(WindowsEvent
| where EventID==4688
| where EventData has_any (".decode('base64')", "base64 --decode", ".decode64(" )
| extend CommandLine = tostring(EventData.CommandLine)
| where isnotempty(CommandLine)
| extend SubjectUserName = tostring(EventData.SubjectUserName)
| extend SubjectDomainName = tostring(EventData.SubjectDomainName)
| extend NewProcessName = tostring(EventData.NewProcessName)
| extend FileName=tostring(split(NewProcessName, '\\')[-1])
| extend ParentProcessName = tostring(EventData.ParentProcessName)
| project TimeGenerated, Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName, CommandLine, ParentProcessName
));
ProcessCreationEvents
| where CommandLine contains ".decode('base64')"
or CommandLine contains "base64 --decode"
or CommandLine contains ".decode64("
| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), CountToday = count() by Computer, Account, AccountDomain, FileName, CommandLine, ParentProcessName
| extend HostName = iif(Computer has '.',substring(Computer,0,indexof(Computer,'.')),Computer) , DnsDomain = iif(Computer has '.',substring(Computer,indexof(Computer,'.')+1),'')
kind: Scheduled
name: Process executed from binary hidden in Base64 encoded file
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint Threat Protection Essentials/Analytic Rules/execute_base64_decodedpayload.yaml
description: |
'Encoding malicious software is a technique used to obfuscate files from detection.
The first CommandLine component is looking for Python decoding base64.
The second CommandLine component is looking for Bash/sh command line base64 decoding.
The third one is looking for Ruby decoding base64.'
status: Available
{
"$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/d6190dde-8fd2-456a-ac5b-0a32400b0464')]",
"kind": "Scheduled",
"name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/d6190dde-8fd2-456a-ac5b-0a32400b0464')]",
"properties": {
"alertRuleTemplateName": "d6190dde-8fd2-456a-ac5b-0a32400b0464",
"customDetails": null,
"description": "'Encoding malicious software is a technique used to obfuscate files from detection. \nThe first CommandLine component is looking for Python decoding base64. \nThe second CommandLine component is looking for Bash/sh command line base64 decoding.\nThe third one is looking for Ruby decoding base64.'\n",
"displayName": "Process executed from binary hidden in Base64 encoded file",
"enabled": true,
"entityMappings": [
{
"entityType": "Account",
"fieldMappings": [
{
"columnName": "Account",
"identifier": "Name"
}
]
},
{
"entityType": "Host",
"fieldMappings": [
{
"columnName": "Computer",
"identifier": "FullName"
},
{
"columnName": "HostName",
"identifier": "HostName"
},
{
"columnName": "DnsDomain",
"identifier": "DnsDomain"
}
]
}
],
"OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Endpoint Threat Protection Essentials/Analytic Rules/execute_base64_decodedpayload.yaml",
"query": "let ProcessCreationEvents=(union isfuzzy=true\n(SecurityEvent\n| where EventID==4688\n| where isnotempty(CommandLine)\n| project TimeGenerated, Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName, FileName = Process, CommandLine, ParentProcessName\n),\n(WindowsEvent\n| where EventID==4688\n| where EventData has_any (\".decode('base64')\", \"base64 --decode\", \".decode64(\" )\n| extend CommandLine = tostring(EventData.CommandLine)\n| where isnotempty(CommandLine)\n| extend SubjectUserName = tostring(EventData.SubjectUserName)\n| extend SubjectDomainName = tostring(EventData.SubjectDomainName)\n| extend NewProcessName = tostring(EventData.NewProcessName)\n| extend FileName=tostring(split(NewProcessName, '\\\\')[-1])\n| extend ParentProcessName = tostring(EventData.ParentProcessName)\n| project TimeGenerated, Computer, Account = SubjectUserName, AccountDomain = SubjectDomainName, CommandLine, ParentProcessName\n));\nProcessCreationEvents \n| where CommandLine contains \".decode('base64')\"\n or CommandLine contains \"base64 --decode\"\n or CommandLine contains \".decode64(\" \n| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), CountToday = count() by Computer, Account, AccountDomain, FileName, CommandLine, ParentProcessName\n| extend HostName = iif(Computer has '.',substring(Computer,0,indexof(Computer,'.')),Computer) , DnsDomain = iif(Computer has '.',substring(Computer,indexof(Computer,'.')+1),'')\n",
"queryFrequency": "P1D",
"queryPeriod": "P1D",
"severity": "Medium",
"status": "Available",
"subTechniques": [],
"suppressionDuration": "PT1H",
"suppressionEnabled": false,
"tactics": [
"DefenseEvasion",
"Execution"
],
"techniques": [
"T1027",
"T1059",
"T1140"
],
"templateVersion": "1.1.3",
"triggerOperator": "GreaterThan",
"triggerThreshold": 0
},
"type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
}
]
}