SSH - Potential Brute Force

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Id	e1ce0eab-10d1-4aae-863f-9a383345ba88
Rulename	SSH - Potential Brute Force
Description	Identifies an IP address that had 15 failed attempts to sign in via SSH in a 4 hour block during a 24 hour time period. Please note that entity mapping for arrays is not supported, so when there is a single value in an array, we will pull that value from the array as a single string to populate the entity to support entity mapping features within Sentinel. Additionally, if the array is multivalued, we will input a string to indicate this with a unique hash so that matching will not occur. As an example - ComputerList is an array that we check for a single value and write that into the HostName field for use in the entity mapping within Sentinel.
Severity	Low
Tactics	CredentialAccess
Techniques	T1110
Required data connectors	Syslog SyslogAma
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/Syslog/Analytic Rules/ssh_potentialBruteForce.yaml
Version	1.1.4
Arm template	e1ce0eab-10d1-4aae-863f-9a383345ba88.json

KQL


let threshold = 15;
Syslog
| where ProcessName =~ "sshd" 
| where SyslogMessage contains "Failed password for invalid user"
| parse kind=relaxed SyslogMessage with * "invalid user " user " from " ip " port" port " ssh2" *
// using distinct below as it has been seen that Syslog can duplicate entries depending on implementation
| distinct TimeGenerated, Computer, user, ip, port, SyslogMessage, _ResourceId
| summarize EventTimes = make_list(TimeGenerated), PerHourCount = count() by bin(TimeGenerated,4h), ip, Computer, user, _ResourceId
| where PerHourCount > threshold
| mvexpand EventTimes
| extend EventTimes = tostring(EventTimes) 
| summarize StartTime = min(EventTimes), EndTime = max(EventTimes), UserList = make_set(user), ComputerList = make_set(Computer), ResourceIdList = make_set(_ResourceId), sum(PerHourCount) by IPAddress = ip
// bringing through single computer and user if array only has 1, otherwise, referencing the column and hashing the ComputerList or UserList so we don't get accidental entity matches when reviewing alerts
| extend HostName = iff(array_length(ComputerList) == 1, tostring(ComputerList[0]), strcat("SeeComputerListField","_", tostring(hash(tostring(ComputerList)))))
| extend Account = iff(array_length(ComputerList) == 1, tostring(UserList[0]), strcat("SeeUserListField","_", tostring(hash(tostring(UserList)))))
| extend ResourceId = iff(array_length(ResourceIdList) == 1, tostring(ResourceIdList[0]), strcat("SeeResourceIdListField","_", tostring(hash(tostring(ResourceIdList)))))

YAML

severity: Low
relevantTechniques:
- T1110
queryFrequency: 1d
kind: Scheduled
version: 1.1.4
triggerOperator: gt
description: |
  'Identifies an IP address that had 15 failed attempts to sign in via SSH in a 4 hour block during a 24 hour time period.
   Please note that entity mapping for arrays is not supported, so when there is a single value in an array, we will pull that value from the array as a single string to populate the entity to support entity mapping features within Sentinel. Additionally, if the array is multivalued, we will input a string to indicate this with a unique hash so that matching will not occur.
   As an example - ComputerList is an array that we check for a single value and write that into the HostName field for use in the entity mapping within Sentinel.'  
queryPeriod: 1d
id: e1ce0eab-10d1-4aae-863f-9a383345ba88
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: Account
    identifier: Name
- entityType: IP
  fieldMappings:
  - columnName: IPAddress
    identifier: Address
- entityType: Host
  fieldMappings:
  - columnName: HostName
    identifier: HostName
- entityType: AzureResource
  fieldMappings:
  - columnName: ResourceId
    identifier: ResourceId
tactics:
- CredentialAccess
name: SSH - Potential Brute Force
triggerThreshold: 0
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Syslog/Analytic Rules/ssh_potentialBruteForce.yaml
query: |2

  let threshold = 15;
  Syslog
  | where ProcessName =~ "sshd" 
  | where SyslogMessage contains "Failed password for invalid user"
  | parse kind=relaxed SyslogMessage with * "invalid user " user " from " ip " port" port " ssh2" *
  // using distinct below as it has been seen that Syslog can duplicate entries depending on implementation
  | distinct TimeGenerated, Computer, user, ip, port, SyslogMessage, _ResourceId
  | summarize EventTimes = make_list(TimeGenerated), PerHourCount = count() by bin(TimeGenerated,4h), ip, Computer, user, _ResourceId
  | where PerHourCount > threshold
  | mvexpand EventTimes
  | extend EventTimes = tostring(EventTimes) 
  | summarize StartTime = min(EventTimes), EndTime = max(EventTimes), UserList = make_set(user), ComputerList = make_set(Computer), ResourceIdList = make_set(_ResourceId), sum(PerHourCount) by IPAddress = ip
  // bringing through single computer and user if array only has 1, otherwise, referencing the column and hashing the ComputerList or UserList so we don't get accidental entity matches when reviewing alerts
  | extend HostName = iff(array_length(ComputerList) == 1, tostring(ComputerList[0]), strcat("SeeComputerListField","_", tostring(hash(tostring(ComputerList)))))
  | extend Account = iff(array_length(ComputerList) == 1, tostring(UserList[0]), strcat("SeeUserListField","_", tostring(hash(tostring(UserList)))))
  | extend ResourceId = iff(array_length(ResourceIdList) == 1, tostring(ResourceIdList[0]), strcat("SeeResourceIdListField","_", tostring(hash(tostring(ResourceIdList)))))
requiredDataConnectors:
- dataTypes:
  - Syslog
  connectorId: Syslog
- dataTypes:
  - Syslog
  connectorId: SyslogAma

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/e1ce0eab-10d1-4aae-863f-9a383345ba88')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/e1ce0eab-10d1-4aae-863f-9a383345ba88')]",
      "properties": {
        "alertRuleTemplateName": "e1ce0eab-10d1-4aae-863f-9a383345ba88",
        "customDetails": null,
        "description": "'Identifies an IP address that had 15 failed attempts to sign in via SSH in a 4 hour block during a 24 hour time period.\n Please note that entity mapping for arrays is not supported, so when there is a single value in an array, we will pull that value from the array as a single string to populate the entity to support entity mapping features within Sentinel. Additionally, if the array is multivalued, we will input a string to indicate this with a unique hash so that matching will not occur.\n As an example - ComputerList is an array that we check for a single value and write that into the HostName field for use in the entity mapping within Sentinel.'\n",
        "displayName": "SSH - Potential Brute Force",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "Account",
                "identifier": "Name"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "IPAddress",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "HostName",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "AzureResource",
            "fieldMappings": [
              {
                "columnName": "ResourceId",
                "identifier": "ResourceId"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Syslog/Analytic Rules/ssh_potentialBruteForce.yaml",
        "query": "\nlet threshold = 15;\nSyslog\n| where ProcessName =~ \"sshd\" \n| where SyslogMessage contains \"Failed password for invalid user\"\n| parse kind=relaxed SyslogMessage with * \"invalid user \" user \" from \" ip \" port\" port \" ssh2\" *\n// using distinct below as it has been seen that Syslog can duplicate entries depending on implementation\n| distinct TimeGenerated, Computer, user, ip, port, SyslogMessage, _ResourceId\n| summarize EventTimes = make_list(TimeGenerated), PerHourCount = count() by bin(TimeGenerated,4h), ip, Computer, user, _ResourceId\n| where PerHourCount > threshold\n| mvexpand EventTimes\n| extend EventTimes = tostring(EventTimes) \n| summarize StartTime = min(EventTimes), EndTime = max(EventTimes), UserList = make_set(user), ComputerList = make_set(Computer), ResourceIdList = make_set(_ResourceId), sum(PerHourCount) by IPAddress = ip\n// bringing through single computer and user if array only has 1, otherwise, referencing the column and hashing the ComputerList or UserList so we don't get accidental entity matches when reviewing alerts\n| extend HostName = iff(array_length(ComputerList) == 1, tostring(ComputerList[0]), strcat(\"SeeComputerListField\",\"_\", tostring(hash(tostring(ComputerList)))))\n| extend Account = iff(array_length(ComputerList) == 1, tostring(UserList[0]), strcat(\"SeeUserListField\",\"_\", tostring(hash(tostring(UserList)))))\n| extend ResourceId = iff(array_length(ResourceIdList) == 1, tostring(ResourceIdList[0]), strcat(\"SeeResourceIdListField\",\"_\", tostring(hash(tostring(ResourceIdList)))))\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Low",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CredentialAccess"
        ],
        "techniques": [
          "T1110"
        ],
        "templateVersion": "1.1.4",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}