Azure DevOps Build Variable Modified by New User

Status: available
Severity: medium
Time window: 14d
Source: github.com/Azure/Azure-Sentinel

'Variables can be configured and used at any stage of the build process in Azure DevOps to inject values. An attacker with the required permissions could modify or add to these variables to conduct malicious activity such as changing paths or remote endpoints called during the build. As variables are often changed by users, just detecting these changes would have a high false positive rate. This detection looks for modifications to variable groups where that user has not been observed modifying them before.'

MITRE ATT&CK coverage

Tactic	Techniques
Defense Impairment	`T1578` Modify Cloud Compute Infrastructure

Rule body kusto

id: 3b9a44d7-c651-45ed-816c-eae583a6f2f1
name: Azure DevOps Build Variable Modified by New User
description: |
  'Variables can be configured and used at any stage of the build process in Azure DevOps to inject values. An attacker with the required permissions could modify or add to these variables to conduct malicious activity such as changing paths or remote endpoints called during the build.
  As variables are often changed by users, just detecting these changes would have a high false positive rate. This detection looks for modifications to variable groups where that user has not been observed modifying them before.'
severity: Medium
status: Available
requiredDataConnectors: []
queryFrequency: 1d
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - DefenseEvasion
relevantTechniques:
  - T1578
query: |
  let lookback = 14d;
  let timeframe = 1d;
  let historical_data =
  ADOAuditLogs
  | where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)
  | where OperationName =~ "Library.VariableGroupModified"
  | extend variables = Data.Variables
  | extend VariableGroupId = tostring(Data.VariableGroupId)
  | extend UserKey = strcat(VariableGroupId, "-", ActorUserId)
  | project UserKey;
  ADOAuditLogs
  | where TimeGenerated > ago(timeframe)
  | where OperationName =~ "Library.VariableGroupModified"
  | extend VariableGroupName = tostring(Data.VariableGroupName)
  | extend VariableGroupId = tostring(Data.VariableGroupId)
  | extend UserKey = strcat(VariableGroupId, "-", ActorUserId)
  | where UserKey !in (historical_data)
  | project-away UserKey
  | project-reorder TimeGenerated, VariableGroupName, ActorUPN, IpAddress, UserAgent
  | extend timestamp = TimeGenerated
  | extend AccountName = tostring(split(ActorUPN, "@")[0]), AccountUPNSuffix = tostring(split(ActorUPN, "@")[1])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: ActorUPN
      - identifier: Name
        columnName: AccountName
      - identifier: UPNSuffix
        columnName: AccountUPNSuffix
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IpAddress
version: 1.0.6
kind: Scheduled

Stages and Predicates

Parameters

let lookback = 14d;
let timeframe = 1d;

Let binding: `historical_data`

let historical_data = ADOAuditLogs
| where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)
| where OperationName =~ "Library.VariableGroupModified"
| extend variables = Data.Variables
| extend VariableGroupId = tostring(Data.VariableGroupId)
| extend UserKey = strcat(VariableGroupId, "-", ActorUserId)
| project UserKey;

Derived from lookback, timeframe.

Stage 1: `source`

ADOAuditLogs

Stage 2: `where`

| where TimeGenerated > ago(timeframe)

Stage 3: `where`

| where OperationName =~ "Library.VariableGroupModified"

Stage 4: `extend` (3 consecutive steps)

| extend VariableGroupName = tostring(Data.VariableGroupName)
| extend VariableGroupId = tostring(Data.VariableGroupId)
| extend UserKey = strcat(VariableGroupId, "-", ActorUserId)

Stage 5: `where`

| where UserKey !in (historical_data)

References historical_data (defined above).

Stage 6: `project-away`

| project-away UserKey

Stage 7: `project-reorder`

| project-reorder TimeGenerated, VariableGroupName, ActorUPN, IpAddress, UserAgent

Stage 8: `extend`

| extend timestamp = TimeGenerated

Stage 9: `extend`

| extend AccountName = tostring(split(ActorUPN, "@")[0]), AccountUPNSuffix = tostring(split(ActorUPN, "@")[1])

Exclusions

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

Field	Kind	Excluded values
`UserKey`	eq	`historical_data`

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
`OperationName`	eq	`Library.VariableGroupModified`

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
`VariableGroupName`	`extend`
`VariableGroupId`	`extend`
`timestamp`	`extend`
`AccountName`	`extend`
`AccountUPNSuffix`	`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)

Azure DevOps Build Variable Modified by New User

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `historical_data`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend` (3 consecutive steps)

Stage 5: `where`

Stage 6: `project-away`

Stage 7: `project-reorder`

Stage 8: `extend`

Stage 9: `extend`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Azure DevOps Build Variable Modified by New User

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: historical_data

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: extend (3 consecutive steps)

Stage 5: where

Stage 6: project-away

Stage 7: project-reorder

Stage 8: extend

Stage 9: extend

Exclusions

Indicators

Output fields

Let binding: `historical_data`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend` (3 consecutive steps)

Stage 5: `where`

Stage 6: `project-away`

Stage 7: `project-reorder`

Stage 8: `extend`

Stage 9: `extend`