Detect abuse of Trusted Relationships (third-party and delegated admin access)

Technique Detected:  Trusted Relationship | T1199

ID: DET0488
Domains: Enterprise
Analytics: AN1344, AN1345, AN1346, AN1347, AN1348, AN1349, AN1350
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

AN1344

Behavioral chain: (1) a login from a third-party account or untrusted source network establishes an interactive/remote session; (2) the session acquires elevated privileges or accesses sensitive resources atypical for that account; (3) subsequent lateral movement or data access occurs from the same session/device. Correlate Windows logon events, token elevation/privileged use, and resource access with third-party context.

Log Sources
Data Component Name Channel
Logon Session Creation (DC0067) WinEventLog:Security EventCode=4624,4648,4672,4769
Logon Session Metadata (DC0088) WinEventLog:Security EventCode=4776,4771,4770
Network Connection Creation (DC0082) WinEventLog:Sysmon EventCode=3
Application Log Content (DC0038) WinEventLog:Security EventCode=4663
Mutable Elements
Field Description
ThirdPartyCIDRs Ranges used by MSPs/contractors/VPN egress; used to enrich logons and network flows.
ExpectedAdminHosts Servers where third-party admins are allowed; deviations raise risk.
TimeWindow Correlation window linking logon → elevation → access (e.g., 30–120 minutes).
HighValueResources File shares/AD objects/servers that should never be touched by third-party sessions.

AN1345

Behavioral chain: (1) sshd or federated SSO logins from third-party networks or identities; (2) rapid sudo/su privilege elevation; (3) access to sensitive paths or east-west SSH. Correlate auth logs, process execution, and network flows.

Log Sources
Data Component Name Channel
Logon Session Metadata (DC0088) auditd:SYSCALL execve,socket,connect,openat
Logon Session Creation (DC0067) linux:syslog Accepted publickey/password for * from * port * ssh2
Network Traffic Content (DC0085) NSM:Flow ssh connections originating from third-party CIDRs
Mutable Elements
Field Description
ThirdPartyUsers POSIX accounts assigned to vendors/partners.
AllowedJumpHosts Bastion hosts permitted for third-party access.
MFAExpected Flag indicating whether PAM/MFA should be present; used to score risk.

AN1346

Behavioral chain: (1) third-party interactive login or mobileconfig-based device enrollment; (2) privilege use or admin group change; (3) lateral movement mounts/ssh. Correlate unified logs and network telemetry.

Log Sources
Data Component Name Channel
Logon Session Creation (DC0067) macos:unifiedlog loginwindow or sshd successful login events
Logon Session Metadata (DC0088) macos:unifiedlog Group membership change for admin or wheel
Network Traffic Content (DC0085) NSM:Flow ssh/smb connections to internal resources from third-party devices
Mutable Elements
Field Description
ManagedDeviceList Known corp devices; treat unknown devices as higher risk.

AN1347

Behavioral chain: (1) delegated admin or external identity establishes session (e.g., partner/reseller DAP, B2B guest, SAML/OAuth trust); (2) role elevation or app consent/permission grant; (3) downstream privileged actions in the tenant. Correlate IdP sign-in, admin/role assignment, and consent/admin-on-behalf events.

Log Sources
Data Component Name Channel
Logon Session Creation (DC0067) azure:signinlogs InteractiveUser, ServicePrincipalSignIn
Logon Session Metadata (DC0088) azure:audit Add delegated admin / Assign admin roles / Update application consent
Application Log Content (DC0038) m365:unified Set-PartnerOfRecord / CompanyAdministrator role assignments / New-DelegatedAdminRelationship
Mutable Elements
Field Description
TrustedPartnerTenantIDs Tenant IDs of approved partners; any others are suspicious.
RequiredMFA Require MFA for partner sessions; alert on bypass or step-up failure.
RoleScopeAllowList Roles third-parties may hold (e.g., Helpdesk Admin); flag broader scopes.

AN1348

Behavioral chain: (1) cross-account or third-party principal assumes a role into the tenant/subscription/project; (2) privileged API calls are made in short succession; (3) access originates from unfamiliar networks or geos. Correlate assume-role/federation events with sensitive API usage.

Log Sources
Data Component Name Channel
Logon Session Creation (DC0067) AWS:CloudTrail AssumeRole,AssumeRoleWithSAML,AssumeRoleWithWebIdentity
Application Log Content (DC0038) AWS:CloudTrail CreateUser|AttachRolePolicy|CreateAccessKey|UpdateAssumeRolePolicy|CreateLoginProfile
Logon Session Metadata (DC0088) gcp:audit google.iam.credentials.generateAccessToken / serviceAccountTokenCreator
Mutable Elements
Field Description
ExternalAccountAllowList Cross-account principals permitted to assume roles; used for allow-listing.
SensitiveAPIs Provider-specific list of risky APIs for scoring.
GeoVelocityThreshold Detect impossible travel between partner and tenant actions.

AN1349

Behavioral chain: (1) third-party app or admin connects via OAuth/marketplace install; (2) high-privilege scopes granted; (3) anomalous actions (mass read/exports, admin changes).

Log Sources
Data Component Name Channel
Application Log Content (DC0038) saas:googleworkspace OAuth2 authorization grants / Admin role assignments
Logon Session Metadata (DC0088) saas:salesforce ConnectedApp OAuth policy change / Login as user
Mutable Elements
Field Description
ApprovedApps Catalog of sanctioned third-party apps and scopes.
ExportVolumeThreshold Data export size/rate baselines to detect abnormal partner activity.

AN1350

Behavioral chain: (1) delegated administration offers/relationships created or modified by partner tenants; (2) mailbox delegation/impersonation enabled; (3) follow-on access from partner IPs.

Log Sources
Data Component Name Channel
Application Log Content (DC0038) m365:unified Add-DelegatedAdmin, Set-PartnerOfRecord, Add-MailboxPermission, Set-OrganizationRelationship
Logon Session Creation (DC0067) azure:signinlogs InteractiveUser, NonInteractiveUser
Mutable Elements
Field Description
MailboxDelegateAllowList Specific mailboxes third-parties may manage.