| Fitbit Inspire 4 (FB423)
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Security Grade
Calculator v1
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Fitbit Inspire 4
Release Date: 2024-03-05 • Status: In sale
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Security Evaluation
1. Device Security
| Criterion
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Value
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Proof
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Comment
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| Known hardware tampering
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Rare
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🔗 Proof
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Hardware modding, custom firmware for Inspire 4 is uncommon; few public hardware hack projects.
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| Known vulnerabilities
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Rare
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🔗 Proof
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Only a small number of Bluetooth pairing and data leakage related Fitbit-family vulnerabilities reported; few CVEs specifically for Inspire 4.
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| Prior attacks
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None
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🔗 Proof
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No public documented targeted attacks against Fitbit Inspire 4.
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| Updatability
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Very common
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🔗 Proof
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Fitbit regularly pushes OTA firmware updates via Fitbit App for function improvement and security fixes.
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| Category Score
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Score: 2 / 3
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2. System Security
| Criterion
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Value
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Proof
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Comment
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| Authentication with other systems
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Partial
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🔗 Proof
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Authenticates and pairs with Fitbit mobile App, linked to Google account; does not support third-party enterprise identity systems.
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| Communications
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Encrypted with up-to-date encryption
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🔗 Proof
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BLE communication between tracker and phone uses modern encryption for health data transmission.
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| Storage
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Encrypted with up-to-date encryption
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🔗 Proof
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Local health data stored on the device flash is encrypted at rest.
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| Category Score
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Score: 2 / 3
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3. User Authentication
| Criterion
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Value
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Proof
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Comment
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| Account management
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Basic
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🔗 Proof
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User identity managed by Google/Fitbit cloud account, the tracker itself has no independent local accounts.
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| Authentication
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Secure
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🔗 Proof
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Device pairing uses BLE secure pairing, bound to verified Fitbit/Google account.
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| Brute-force protection
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Exist
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🔗 Proof
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Rate-limiting on pairing attempts to block repeated brute force pairing requests.
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| Event logging
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Partial logging
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🔗 Proof
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Activity and sync logs kept in Fitbit cloud backend; limited audit logs stored locally on tracker.
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| Passwords
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Require change after setup with complexity requirements
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🔗 Proof
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Password rules and periodic password management are enforced on the linked Google/Fitbit cloud account side.
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| Category Score
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Score: 2 / 3
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Technical Specifications
| Property
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Details
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| Operating System & App
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Fitbit OS (embedded lightweight wearable firmware) (Companion App: Fitbit App)
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| Hardware (CPU / GPU)
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CPU: Nordic nRF52840 (BLE system-on-chip) • GPU: No dedicated GPU
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| Memory & Storage
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Memory: On-chip RAM for firmware and temporary health data cache • Storage: On-board flash storage for local activity/heart-rate records
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| Power, Battery & Charging
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Battery: Lithium-polymer rechargeable battery • Power: 3.7 V DC • Charging: Magnetic dedicated charging cable
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| Display & Camera
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Display: 0.74 inch monochrome OLED display • Camera: No camera
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| Sound & Connectivity
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Sound: No speaker or microphone • Connectivity: Bluetooth Low Energy (BLE 5.0)
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| Physical (Dimensions & Mass)
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Dimensions: 18.7 × 45.1 × 11.8 mm • Mass: 26 g (including band)
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Fitbit Inspire 4 (FB423) is a lightweight wearable fitness tracker from Fitbit (Google). It runs Fitbit embedded OS, connects to the Fitbit mobile App over BLE for synchronising heart rate, sleep and activity metrics. Bluetooth communication and local stored health data are encrypted. It supports regular OTA firmware updates. User identity relies on a linked Google/Fitbit cloud account, with secure BLE pairing and brute-force protection for pairing. Public exploits and hardware tampering cases for this model are rare.
