# T1534 - Internal Spearphishing

## SOC Recommendation
Investigate Internal Spearphishing activity in the context of Lateral Movement: confirm scope, affected host/identity, and whether it matches expected administrative behaviour before deciding this is benign.

## D3FEND Mappings
| D3FEND Technique | Relationship | Practical SOC Action |
|---|---|---|
| File Analysis | Detect | Monitor for File Analysis indicators relevant to this technique. |
| File Encryption | Harden | Apply File Encryption to reduce this technique's viability before an incident occurs. |
| File Eviction | Evict | Use File Eviction to remove the adversary's foothold once this technique is confirmed. |
| Content Filtering | Isolate | Apply Content Filtering to contain the blast radius once this technique is observed. |

## Investigation Steps
1. Review Defender for Endpoint / Defender XDR alerts and timeline for the affected host or identity.
2. Check Sentinel analytics rules and incidents correlated with this technique.
3. Review Entra ID sign-in and audit logs if the technique involves an identity or cloud resource.

## Evidence to Collect
- Host or resource affected
- Account or identity involved
- Timestamp of the activity
- Related process, file, or network artifact
- Any preceding or follow-on alerts

## Response Actions
| Action | Risk | Automation Safe | Approval Required |
|---|---|---|---|
| Contain the affected host or account | Medium | No | Yes |
| Collect and preserve evidence | Low | Yes | No |

## KQL
```kql
MimecastCG
| where Type == "email_iep"
| extend  SenderEnvelope = ['Sender Envelope']  , MessageId = ['Message ID']
```
```kql
MimecastSIEM_CL| where mimecastEventId_s=="mail_ttp_iep"
```
```kql
////////////
// threshold = If the number of unique accounts that a power app is shared with is greater than
// threshold than it'll trigger an alert. A threshold of 5 is good to start with.
// However, if this is giving too many false positives, please adjust the threshold.
////////////
let threshold = 5;
////////////
// Please replace the allowed_domains with a list of domains of your partners/sibling orgs
// with whom you generally share power apps with. This will allow us to filter
// legitimate bulk sharing attempts. Avoid using domains such as gmail, outlook, etc.
///////////
let allowed_domains = pack_array("contoso.com");
let query_frequency = 1h;
let query_lookback = 14d;
PowerPlatformAdminActivity
| where TimeGenerated >= ago(query_frequency)
| where EventOriginalType == "PowerAppPermissionEdited"
| extend Properties = tostring(PropertyCollection)
| extend AppId = extract(@'"powerplatform.analytics.resource.power_app.id","Value":"([^"]+)"', 1, Properties)
| extend AppId = tolower(replace_string(AppId, '/providers/Microsoft.PowerApps/apps/', ''))
| extend TargetPrincipalId = extract(@'"targetuser.id","Value":"([^"]+)"', 1, Properties)
| join kind=leftouter (
    AuditLogs
    | where ActivityDateTime >= ago(query_lookback)
    | where SourceSystem =~ "Azure AD" and OperationName == "Invite external user"
    | where Result =~ "success"
    | extend InvitedOrgEmail = tostring(parse_json(AdditionalDetails[5])['value'])
    | extend InvitedOrgDomain = tostring(split(InvitedOrgEmail, "@")[1])
    | where not(InvitedOrgDomain has_any(allowed_domains))
    | extend
        InvitedById = tostring(parse_json(InitiatedBy)['user']['id']),
        InvitedByUPN = tostring(parse_json(InitiatedBy)['user']['userPrincipalName']),
        InvitedEmail = tostring(parse_json(TargetResources[0])['userPrincipalName']),
        InvitedId = tostring(parse_json(TargetResources[0])['id'])
    | summarize by InvitedById, InvitedByUPN, InvitedEmail, InvitedId, InvitedOrgDomain)
    on $left.TargetPrincipalId == $right.InvitedId
| where isnotempty(InvitedId)
| summarize
    StartTime = min(TimeGenerated),
    EndTime = max(TimeGenerated),
    TargetedUsersCount=dcount(TargetPrincipalId),
    TargetedObjectIds = make_set(TargetPrincipalId, 1000),
    InvitedDomains = make_set(InvitedOrgDomain, 1000),
    InvitedEmailAddresses = make_set(InvitedEmail, 1000)
    by AppId, InvitedById, InvitedByUPN
| extend
    PowerAppsEntityId = 27593,
    AccountName = tostring(split(InvitedByUPN, '@')[0]),
    UPNSuffix = tostring(split(InvitedByUPN, '@')[1])
| project
    StartTime,
    EndTime,
    InvitedByUPN,
    InvitedById,
    InvitedDomains,
    InvitedEmailAddresses,
    TargetedUsersCount,
    TargetedObjectIds,
    AppId,
    PowerAppsEntityId,
    AccountName,
    UPNSuffix
```

## Escalation Criteria
- Internal Spearphishing activity observed on a privileged account or critical system.
- Activity follows or precedes other suspicious behaviour in the same investigation.
- Automated triage cannot confidently rule out malicious intent.

## False Positive Considerations
- Legitimate administrative or maintenance activity matching this pattern.
- Approved security testing or red team exercise.
- Known benign software producing similar telemetry.

Generated by SOC Response Atlas by Basyrix.