Email access via active sync

Severity: medium
Time window: 1d
Author: Microsoft Security Research
Source: github.com/Azure/Azure-Sentinel

This query detects attempts to add attacker devices as allowed IDs for active sync using the Set-CASMailbox command. This technique was seen in relation to Solorigate attack but the results can indicate potential malicious activity used in different attacks. - Note that this query can be changed to use the KQL "has_all" operator, which hasn't yet been documented officially, but will be soon. In short, "has_all" will only match when the referenced field has all strings in the list. - Refer to Set-CASMailbox syntax: https://docs.microsoft.com/powershell/module/exchange/set-casmailbox?view=exchange-ps

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1068` Exploitation for Privilege Escalation, `T1078` Valid Accounts

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation
Security-Auditing	Event ID 4688	A new process has been created.

Rule body kusto

id: 2f561e20-d97b-4b13-b02d-18b34af6e87c
name: Email access via active sync
description: |
   This query detects attempts to add attacker devices as allowed IDs for active sync using the Set-CASMailbox command.
   This technique was seen in relation to Solorigate attack but the results can indicate potential malicious activity used in different attacks.
   - Note that this query can be changed to use the KQL "has_all" operator, which hasn't yet been documented officially, but will be soon.
     In short, "has_all" will only match when the referenced field has all strings in the list.
   - Refer to Set-CASMailbox syntax: https://docs.microsoft.com/powershell/module/exchange/set-casmailbox?view=exchange-ps  
severity: Medium
requiredDataConnectors:
  - connectorId: SecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceProcessEvents
  - connectorId: WindowsSecurityEvents
    dataTypes: 
      - SecurityEvents 
  - connectorId: WindowsForwardedEvents
    dataTypes: 
      - WindowsEvent 
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - PrivilegeEscalation
relevantTechniques:
  - T1068
  - T1078
tags:
  - Solorigate
  - NOBELIUM
query: |
  let timeframe = 1d;
  let cmdList = dynamic(["Set-CASMailbox","ActiveSyncAllowedDeviceIDs","add"]);
  (union isfuzzy=true
  (
  SecurityEvent
  | where TimeGenerated >= ago(timeframe)
  | where EventID == 4688
  | where CommandLine has_all (cmdList)
  | project Type, TimeGenerated, Computer, Account, SubjectDomainName, SubjectUserName, Process, ParentProcessName, CommandLine
  | extend timestamp = TimeGenerated, AccountEntity = Account, HostEntity = Computer
  ),
  ( WindowsEvent
  | where TimeGenerated >= ago(timeframe)
  | where EventID == 4688
  | where EventData has_all (cmdList)
  | extend CommandLine = tostring(EventData.CommandLine) 
  | where CommandLine has_all (cmdList)
  | extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
  | extend SubjectUserName = tostring(EventData.SubjectUserName)
  | extend SubjectDomainName = tostring(EventData.SubjectDomainName)
  | extend NewProcessName = tostring(EventData.NewProcessName)
  | extend Process=tostring(split(NewProcessName, '\\')[-1])
  | extend ParentProcessName = tostring(EventData.ParentProcessName)
  | project Type, TimeGenerated, Computer, Account, SubjectDomainName, SubjectUserName, Process, ParentProcessName, CommandLine
  | extend timestamp = TimeGenerated, AccountEntity = Account, HostEntity = Computer
  ),
  (
  DeviceProcessEvents
  | where TimeGenerated >= ago(timeframe)
  | where InitiatingProcessCommandLine has_all (cmdList)
  | project Type, TimeGenerated, DeviceName, AccountName, InitiatingProcessAccountDomain, InitiatingProcessAccountName, InitiatingProcessFileName, InitiatingProcessParentFileName,  InitiatingProcessCommandLine
  | extend timestamp = TimeGenerated, AccountDomain = InitiatingProcessAccountDomain, AccountName = InitiatingProcessAccountName, HostEntity = DeviceName
  ),
  (
  Event
  | where TimeGenerated > ago(timeframe)
  | where Source == "Microsoft-Windows-Sysmon"
  | where EventID == 1
  | extend EventData = parse_xml(EventData).DataItem.EventData.Data
  | mv-expand bagexpansion=array EventData
  | evaluate bag_unpack(EventData)
  | extend Key=tostring(['@Name']), Value=['#text']
  | evaluate pivot(Key, any(Value), TimeGenerated, Source, EventLog, Computer, EventLevel, EventLevelName, EventID, UserName, RenderedDescription, MG, ManagementGroupName, Type, _ResourceId)
  | where TimeGenerated >= ago(timeframe)
  | where CommandLine has_all (cmdList)
  | extend Type = strcat(Type, ": ", Source)
  | project Type, TimeGenerated, Computer, User, Process, ParentImage, CommandLine
  | extend timestamp = TimeGenerated, AccountEntity = User, HostEntity = Computer
  )
  )
  | extend HostName = tostring(split(HostEntity, ".")[0]), DomainIndex = toint(indexof(HostEntity, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(HostEntity, DomainIndex + 1), HostEntity)
  | extend AccountName = tostring(split(AccountEntity, @'\')[1]), AccountDomain = tostring(split(AccountEntity, @'\')[0])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: AccountEntity
      - identifier: Name
        columnName: AccountName
      - identifier: NTDomain
        columnName: AccountDomain
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: HostEntity
      - identifier: HostName
        columnName: HostName
      - identifier: NTDomain
        columnName: HostNameDomain
version: 1.2.1
kind: Scheduled
metadata:
    source:
        kind: Community
    author:
        name: Microsoft Security Research
    support:
        tier: Community
    categories:
        domains: [ "Security - Threat Protection" ]

Stages and Predicates

Parameters

let timeframe = 1d;
let cmdList = dynamic(["Set-CASMailbox","ActiveSyncAllowedDeviceIDs","add"]);

union `isfuzzy=true` (4 sources)

Each leg below queries one source; the rule matches if any leg does. Sources: SecurityEvent, WindowsEvent, DeviceProcessEvents, Event

Leg 1: `SecurityEvent`

SecurityEvent
| where TimeGenerated >= ago(timeframe)
| where EventID == 4688
| where CommandLine has_all (cmdList)
| project Type, TimeGenerated, Computer, Account, SubjectDomainName, SubjectUserName, Process, ParentProcessName, CommandLine
| extend timestamp = TimeGenerated, AccountEntity = Account, HostEntity = Computer

Leg 2: `WindowsEvent`

WindowsEvent
| where TimeGenerated >= ago(timeframe)
| where EventID == 4688
| where EventData has_all (cmdList)
| extend CommandLine = tostring(EventData.CommandLine) 
| where CommandLine has_all (cmdList)
| extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
| extend SubjectUserName = tostring(EventData.SubjectUserName)
| extend SubjectDomainName = tostring(EventData.SubjectDomainName)
| extend NewProcessName = tostring(EventData.NewProcessName)
| extend Process=tostring(split(NewProcessName, '\\')[-1])
| extend ParentProcessName = tostring(EventData.ParentProcessName)
| project Type, TimeGenerated, Computer, Account, SubjectDomainName, SubjectUserName, Process, ParentProcessName, CommandLine
| extend timestamp = TimeGenerated, AccountEntity = Account, HostEntity = Computer

Leg 3: `DeviceProcessEvents`

DeviceProcessEvents
| where TimeGenerated >= ago(timeframe)
| where InitiatingProcessCommandLine has_all (cmdList)
| project Type, TimeGenerated, DeviceName, AccountName, InitiatingProcessAccountDomain, InitiatingProcessAccountName, InitiatingProcessFileName, InitiatingProcessParentFileName,  InitiatingProcessCommandLine
| extend timestamp = TimeGenerated, AccountDomain = InitiatingProcessAccountDomain, AccountName = InitiatingProcessAccountName, HostEntity = DeviceName

Leg 4: `Event`

Event
| where TimeGenerated > ago(timeframe)
| where Source == "Microsoft-Windows-Sysmon"
| where EventID == 1
| extend EventData = parse_xml(EventData).DataItem.EventData.Data
| mv-expand bagexpansion=array EventData
| evaluate bag_unpack(EventData)
| extend Key=tostring(['@Name']), Value=['#text']
| evaluate pivot(Key, any(Value), TimeGenerated, Source, EventLog, Computer, EventLevel, EventLevelName, EventID, UserName, RenderedDescription, MG, ManagementGroupName, Type, _ResourceId)
| where TimeGenerated >= ago(timeframe)
| where CommandLine has_all (cmdList)
| extend Type = strcat(Type, ": ", Source)
| project Type, TimeGenerated, Computer, User, Process, ParentImage, CommandLine
| extend timestamp = TimeGenerated, AccountEntity = User, HostEntity = Computer

Applied to the combined result

| extend HostName = tostring(split(HostEntity, ".")[0]), DomainIndex = toint(indexof(HostEntity, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(HostEntity, DomainIndex + 1), HostEntity)
| extend AccountName = tostring(split(AccountEntity, @'\')[1]), AccountDomain = tostring(split(AccountEntity, @'\')[0])

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
`CommandLine`	match	`ActiveSyncAllowedDeviceIDs` `Set-CASMailbox` `add` corpus 34 (sigma 26, splunk 4, chronicle 2, kusto 2)
`EventData`	match	`ActiveSyncAllowedDeviceIDs` `Set-CASMailbox` `add`
`EventID`	eq	`1` transforms: `cased` corpus 237 (splunk 224, kusto 13) `4688` transforms: `cased` corpus 313 (splunk 283, kusto 30)
`InitiatingProcessCommandLine`	match	`ActiveSyncAllowedDeviceIDs` `Set-CASMailbox` `add` corpus 34 (sigma 26, splunk 4, chronicle 2, kusto 2)

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
`CommandLine`	`project`
`Computer`	`project`
`ParentImage`	`project`
`Process`	`project`
`TimeGenerated`	`project`
`Type`	`project`
`User`	`project`
`AccountEntity`	`extend`
`HostEntity`	`extend`
`timestamp`	`extend`
`DomainIndex`	`extend`
`HostName`	`extend`
`HostNameDomain`	`extend`
`AccountDomain`	`extend`
`AccountName`	`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)

Email access via active sync

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

union `isfuzzy=true` (4 sources)

Leg 1: `SecurityEvent`

Leg 2: `WindowsEvent`

Leg 3: `DeviceProcessEvents`

Leg 4: `Event`

Applied to the combined result

Indicators

Output fields

Keyboard shortcuts

Search operators

Email access via active sync

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

union isfuzzy=true (4 sources)

Leg 1: SecurityEvent

Leg 2: WindowsEvent

Leg 3: DeviceProcessEvents

Leg 4: Event

Applied to the combined result

Indicators

Output fields

union `isfuzzy=true` (4 sources)

Leg 1: `SecurityEvent`

Leg 2: `WindowsEvent`

Leg 3: `DeviceProcessEvents`

Leg 4: `Event`