Password Spraying

Status: available
Severity: medium
Time window: 1d
Group by: DeviceName, RemoteIP
Source: github.com/Azure/Azure-Sentinel

This query detects a password spraying attack, where a single machine has performed a large number of failed login attempts, with a large number of different accounts. For each account, the attacker uses just a few attempts to prevent account lockout. This query uses the DeviceLogonEvents per machine to detect a password spraying attacks. The machine against which the password spraying is performed (can be DC, a server or even an endpoint) needs to be enrolled in Microsoft Defender for Endpoint.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1110.003` Brute Force: Password Spraying

Telemetry coverage

Platform	Record / event type
Microsoft Defender for Endpoint	`DeviceLogonEvents` action `LogonFailed`: Logon failed
Microsoft Defender for Endpoint	`DeviceLogonEvents` action `LogonSuccess`: Logon succeeded

Rule body

id: e00f72ab-fea1-4a31-9ecc-eea6397cd38d
name: Password Spraying
description: |
  This query detects a password spraying attack, where a single machine has performed a large number of failed login attempts, with a large number of different accounts. 
  For each account, the attacker uses just a few attempts to prevent account lockout. This query uses the DeviceLogonEvents per machine to detect a password spraying attacks. 
  The machine against which the password spraying is performed (can be DC, a server or even an endpoint) needs to be enrolled in Microsoft Defender for Endpoint.
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceLogonEvents
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110.003
query: |
  let thresholdForUniqueFailedAccounts = 20;
  let upperBoundOfFailedLogonsPerAccount = 10;
  let ratioSuccessFailedLogons = 0.5;
  let timeframe = 1d;
  DeviceLogonEvents
  | where Timestamp >= ago(timeframe)
  | where LogonType != "Unlock" and ActionType in ("LogonSuccess", "LogonFailed")
  | where not(isempty( RemoteIP) and isempty( RemoteDeviceName))
  | extend LocalLogon=parse_json(AdditionalFields)
  | where RemoteIPType != "Loopback"
  | summarize SuccessLogonCount = countif(ActionType == "LogonSuccess"), FailedLogonCount = countif(ActionType == "LogonFailed"),
      UniqueAccountFailedLogons=dcountif(AccountName, ActionType == "LogonFailed"), FirstFailed=minif(Timestamp, ActionType == "LogonFailed"),
      LastFailed=maxif(Timestamp, ActionType == "LogonFailed"), LastTimestamp=arg_max(Timestamp, tostring(ReportId)) by RemoteIP, DeviceName // RemoteIP is the source of the logon attempt.
  | project-rename IPAddress=RemoteIP
  | where UniqueAccountFailedLogons > thresholdForUniqueFailedAccounts and SuccessLogonCount*ratioSuccessFailedLogons < FailedLogonCount and UniqueAccountFailedLogons*upperBoundOfFailedLogonsPerAccount > FailedLogonCount 
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: DeviceName
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IPAddress 
version: 1.0.1
kind: Scheduled

Stages and Predicates

Parameters

let thresholdForUniqueFailedAccounts = 20;
let upperBoundOfFailedLogonsPerAccount = 10;
let ratioSuccessFailedLogons = 0.5;
let timeframe = 1d;

Stage 1: `source`

DeviceLogonEvents

Stage 2: `where`

| where Timestamp >= ago(timeframe)

Stage 3: `where`

| where LogonType != "Unlock" and ActionType in ("LogonSuccess", "LogonFailed")

Stage 4: `where`

| where not(isempty( RemoteIP) and isempty( RemoteDeviceName))

Stage 5: `extend`

| extend LocalLogon=parse_json(AdditionalFields)

Stage 6: `where`

| where RemoteIPType != "Loopback"

Stage 7: `summarize`

| summarize SuccessLogonCount = countif(ActionType == "LogonSuccess"), FailedLogonCount = countif(ActionType == "LogonFailed"),
    UniqueAccountFailedLogons=dcountif(AccountName, ActionType == "LogonFailed"), FirstFailed=minif(Timestamp, ActionType == "LogonFailed"),
    LastFailed=maxif(Timestamp, ActionType == "LogonFailed"), LastTimestamp=arg_max(Timestamp, tostring(ReportId)) by RemoteIP, DeviceName

Stage 8: `project-rename`

| project-rename IPAddress=RemoteIP

Stage 9: `where`

| where UniqueAccountFailedLogons > thresholdForUniqueFailedAccounts and SuccessLogonCount*ratioSuccessFailedLogons < FailedLogonCount and UniqueAccountFailedLogons*upperBoundOfFailedLogonsPerAccount > FailedLogonCount

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`RemoteDeviceName`	is_null	(no value, null check)	`excludes:RemoteDeviceName`
`RemoteIP`	is_null	(no value, null check)	`excludes:RemoteIP`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ActionType`	in	`LogonFailed` `LogonSuccess` corpus 6 (kusto 6)	`field:"ActionType" kind:in`
`LogonType`	ne	`Unlock`	`field:"LogonType" kind:ne value:"Unlock"`
`RemoteIPType`	ne	`Loopback` corpus 3 (kusto 3)	`field:"RemoteIPType" kind:ne value:"Loopback"`
`SuccessLogonCount`	cross_field_compare	`FailedLogonCount` transforms: `op:lt`, `lhs:mul:0.5`	`field:"SuccessLogonCount" kind:cross_field_compare value:"FailedLogonCount"`
`UniqueAccountFailedLogons`	cross_field_compare	`FailedLogonCount` transforms: `op:gt`, `lhs:mul:10`	`field:"UniqueAccountFailedLogons" kind:cross_field_compare value:"FailedLogonCount"`
`UniqueAccountFailedLogons`	gt	`20`	`field:"UniqueAccountFailedLogons" kind:gt value:"20"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`DeviceName`	`summarize`
`FailedLogonCount`	`summarize`
`FirstFailed`	`summarize`
`LastFailed`	`summarize`
`LastTimestamp`	`summarize`
`RemoteIP`	`summarize`
`SuccessLogonCount`	`summarize`
`UniqueAccountFailedLogons`	`summarize`
`IPAddress`	`project-rename`

Password Spraying

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: extend

Stage 6: where

Stage 7: summarize

Stage 8: project-rename

Stage 9: where