Potential Build Process Compromise - MDE

Status: available
Severity: medium
Time window: 5m
Group by: BuildAccount, BuildCommand, BuildParentProcess, BuildProcess, BuildProcessTime, DeviceName, FileEditAccount, FileEditDomain, FileEditUpn, timekey
Source: github.com/Azure/Azure-Sentinel

The query looks for source code files being modified immediately after a build process is started. The purpose of this is to look for malicious code injection during the build process. This query uses Microsoft Defender for Endpoint telemetry. More details: https://techcommunity.microsoft.com/t5/azure-sentinel/monitoring-the-software-supply-chain-with-azure-sentinel/ba-p/2176463

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1554` Compromise Host Software Binary

Event coverage

Provider	Event/ActionType	Title
Sysmon	Event ID 1	Process creation
Security-Auditing	Event ID 4688	A new process has been created.
Defender-DeviceProcessEvents	any	Process activity (any)

Rule body kusto

id: 1bf6e165-5e32-420e-ab4f-0da8558a8be2
name: Potential Build Process Compromise - MDE
description: |
  'The query looks for source code files being modified immediately after a build process is started. The purpose of this is to look for malicious code injection during the build process. This query uses Microsoft Defender for Endpoint telemetry.
  More details: https://techcommunity.microsoft.com/t5/azure-sentinel/monitoring-the-software-supply-chain-with-azure-sentinel/ba-p/2176463'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceProcessEvents
      - DeviceFileEvents
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Persistence
relevantTechniques:
  - T1554
tags:
  - Solorigate
  - NOBELIUM
query: |
  // How far back to look for events from
  let timeframe = 1d;
  // How close together build events and file modifications should occur to alert (make this smaller to reduce FPs)
  let time_window = 5m;
  // Edit this to include build processes used
  let build_processes = dynamic(["MSBuild.exe", "dotnet.exe", "VBCSCompiler.exe"]);
  // Include any processes that you want to allow to edit files during/around the build process
  let allow_list = dynamic([]);
  DeviceProcessEvents
  | where TimeGenerated > ago(timeframe)
  // Look for build process starts
  | where FileName has_any (build_processes)
  | summarize by BuildParentProcess=InitiatingProcessFileName, BuildProcess=FileName, BuildAccount = AccountName, DeviceName, BuildCommand=ProcessCommandLine, 
  timekey= bin(TimeGenerated, time_window), BuildProcessTime=TimeGenerated
  | join kind=inner(
  DeviceFileEvents
  | where TimeGenerated > ago(timeframe)
  | where InitiatingProcessFileName !in (allow_list)
  | where ActionType == "FileCreated"  or ActionType == "FileModified"
  // Look for code files, edit this to include file extensions used in build.
  | where FileName endswith ".cs" or FileName endswith ".cpp"
  | summarize by FileEditParentProcess=InitiatingProcessParentFileName, FileEditAccount = InitiatingProcessAccountName, FileEditDomain = InitiatingProcessAccountDomain, FileEditUpn = InitiatingProcessAccountUpn, 
  DeviceName, FileEdited=FileName, FileEditProcess=InitiatingProcessFileName, timekey= bin(TimeGenerated, time_window), FileEditTime=TimeGenerated)
  // join where build processes and file modifications seen at same time on same host
  on timekey, DeviceName
  // Limit to only where the file edit happens after the build process starts
  | where BuildProcessTime <= FileEditTime
  | summarize make_set(FileEdited), make_set(FileEditProcess) by timekey, DeviceName, BuildParentProcess, BuildProcess, FileEditAccount, FileEditDomain, FileEditUpn
  | extend HostName = tostring(split(DeviceName, ".")[0]), DomainIndex = toint(indexof(DeviceName, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(DeviceName, DomainIndex + 1), DeviceName)
entityMappings:
  - entityType: Host
    fieldMappings:
    - identifier: HostName
      columnName: HostName
    - identifier: DnsDomain
      columnName: HostNameDomain
  - entityType: Account
    fieldMappings:
    - identifier: FullName
      columnName: FileEditUpn
    - identifier: Name
      columnName: FileEditAccount
    - identifier: UPNSuffix
      columnName: FileEditDomain
version: 1.1.0
kind: Scheduled

Stages and Predicates

Parameters

let timeframe = 1d;
let time_window = 5m;
let build_processes = dynamic(["MSBuild.exe", "dotnet.exe", "VBCSCompiler.exe"]);
let allow_list = dynamic([]);

Stage 1: `source`

DeviceProcessEvents

Stage 2: `where`

| where TimeGenerated > ago(timeframe)

Stage 3: `where`

| where FileName has_any (build_processes)

Stage 4: `summarize`

| summarize by BuildParentProcess=InitiatingProcessFileName, BuildProcess=FileName, BuildAccount = AccountName, DeviceName, BuildCommand=ProcessCommandLine, 
timekey= bin(TimeGenerated, time_window), BuildProcessTime=TimeGenerated

Stage 5: `join`

| join kind=inner(
DeviceFileEvents
| where TimeGenerated > ago(timeframe)
| where InitiatingProcessFileName !in (allow_list)
| where ActionType == "FileCreated"  or ActionType == "FileModified"
| where FileName endswith ".cs" or FileName endswith ".cpp"
| summarize by FileEditParentProcess=InitiatingProcessParentFileName, FileEditAccount = InitiatingProcessAccountName, FileEditDomain = InitiatingProcessAccountDomain, FileEditUpn = InitiatingProcessAccountUpn, 
DeviceName, FileEdited=FileName, FileEditProcess=InitiatingProcessFileName, timekey= bin(TimeGenerated, time_window), FileEditTime=TimeGenerated)
on timekey, DeviceName

Stage 6: `where`

| where BuildProcessTime <= FileEditTime

Stage 7: `summarize`

| summarize make_set(FileEdited), make_set(FileEditProcess) by timekey, DeviceName, BuildParentProcess, BuildProcess, FileEditAccount, FileEditDomain, FileEditUpn

Stage 8: `extend`

| extend HostName = tostring(split(DeviceName, ".")[0]), DomainIndex = toint(indexof(DeviceName, '.'))

Stage 9: `extend`

| extend HostNameDomain = iff(DomainIndex != -1, substring(DeviceName, DomainIndex + 1), DeviceName)

HostNameDomain =

ifDomainIndex != -1substring(DeviceName, (DomainIndex + 1))

elseDeviceName

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`InitiatingProcessFileName`	eq	`[]`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`ActionType`	eq	`FileCreated` transforms: `cased` corpus 8 (kusto 8) `FileModified` transforms: `cased`
`BuildProcessTime`	le	`FileEditTime` transforms: `cased` corpus 2 (kusto 2)
`FileName`	ends_with	`.cpp` `.cs`
`FileName`	match	`MSBuild.exe` corpus 2 (kusto 2) `VBCSCompiler.exe` `dotnet.exe`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`BuildParentProcess`	`summarize`
`BuildProcess`	`summarize`
`DeviceName`	`summarize`
`FileEditAccount`	`summarize`
`FileEditDomain`	`summarize`
`FileEditUpn`	`summarize`
`timekey`	`summarize`
`DomainIndex`	`extend`
`HostName`	`extend`
`HostNameDomain`	`extend`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Potential Build Process Compromise - MDE

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `summarize`

Stage 5: `join`

Stage 6: `where`

Stage 7: `summarize`

Stage 8: `extend`

Stage 9: `extend`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Potential Build Process Compromise - MDE

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: summarize

Stage 5: join

Stage 6: where

Stage 7: summarize

Stage 8: extend

Stage 9: extend

Exclusions

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `summarize`

Stage 5: `join`

Stage 6: `where`

Stage 7: `summarize`

Stage 8: `extend`

Stage 9: `extend`