Detection of SSL Pinning

Technique Detected:  SSL Pinning | T1521.003

ID: DET0646
Domains: Mobile
Analytics: AN1725, AN1726
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

AN1725

The defender correlates application TLS trust customization activity with subsequent outbound encrypted sessions that bypass enterprise interception visibility or fail only under enterprise inspection conditions. The analytic looks for an app establishing its own certificate or public-key trust logic, then initiating HTTPS sessions to destinations not aligned with approved app behavior, especially from background state or without recent user interaction. Higher-confidence observations come from Android runtime/framework telemetry showing custom trust manager, certificate validation override, or pin validation logic immediately preceding network connection attempts, combined with network evidence of failed-inspection patterns or opaque direct TLS sessions.

Log Sources
Data Component Name Channel
OS API Execution (DC0021) MobileEDR:telemetry Application invokes custom TLS trust evaluation logic or pin validation routines (e.g., custom TrustManager, HostnameVerifier override, certificate/public key comparison) immediately before outbound TLS session establishment
Application State (DC0123) MobileEDR:telemetry TLS trust customization and outbound HTTPS session occur while app_state=background or device_locked=true or recent_user_interaction=false
Application Permission (DC0114) android:MDMLog Managed app with undeclared secure transport behavior or app category mismatch initiates opaque TLS communications inconsistent with enterprise policy baseline
Network Traffic Content (DC0085) NSM:Flow Application initiates HTTPS connection with repeated certificate validation failure under enterprise proxy followed by direct network retry or stable opaque TLS communication to same endpoint within correlation window
NSM:Inspection TLS session from mobile app fails, resets, or refuses enterprise interception while same destination/app pair repeatedly establishes direct encrypted communication pattern consistent with pinned certificate/public-key validation
Mutable Elements
Field Description
TimeWindow Correlation window between trust customization activity and outbound TLS connection
AllowedAppList Apps legitimately expected to implement SSL pinning such as banking, enterprise auth, or secure messaging apps
AllowedDestinationList Approved domains, IPs, and service endpoints for managed applications
ForegroundStateRequired Whether the application is expected to establish pinned sessions only during active user-driven workflows
InspectionFailureThreshold Number of repeated inspection failures or certificate mismatch events before escalating
RetryPatternWindow Time tolerance for inspection failure followed by retry/direct connection pattern

AN1726

The defender correlates supervised-device application posture and background execution context with network-side evidence that an app rejects enterprise inspection or performs certificate/public-key-bound trust behavior during TLS establishment. Because direct app-level pin-validation observability is weaker on iOS, the analytic is anchored primarily to network control-plane effects: repeated TLS handshake rejection under enterprise inspection, destination-specific inspection bypass patterns, or persistent opaque app-to-endpoint encrypted sessions inconsistent with baseline app behavior. Additional confidence comes from managed app identity, background execution context, and supervised device policy state.

Log Sources
Data Component Name Channel
Application Permission (DC0114) iOS:MDMLog Supervised managed app with undeclared secure transport behavior or unexpected network role communicates with non-baselined destination over opaque TLS
Application State (DC0123) MobileEDR:telemetry Managed app initiates or resumes network-capable execution while app_state=background or device_locked=true before opaque TLS session attempt
Network Traffic Content (DC0085) NSM:Flow App-destination pair shows consistent inspection bypass/refusal pattern followed by direct encrypted communication or repeated short-lived TLS sessions to same endpoint within correlation window
NSM:Inspection TLS handshake from iOS app repeatedly fails or is rejected only when enterprise SSL inspection certificate is presented, indicating certificate or public-key pin validation effect
Mutable Elements
Field Description
TimeWindow Correlation window between app lifecycle event and network-side inspection failure or opaque TLS session
AllowedAppList Managed apps expected to use certificate or public-key pinning for legitimate purposes
AllowedDestinationList Approved endpoints expected for legitimate pinned sessions
ForegroundStateRequired Whether the app is expected to perform network establishment only during user-driven workflows
InspectionFailureThreshold Number of repeated TLS-inspection failures needed before escalating confidence