Microsoft Sentinel medium experimental kql

Email access via active sync

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

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Detection Logic

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])

Field Validations

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