counter-surveillance

# Counter-Surveillance Security Skill Trail of Bits-style defensive security assessment focused on surveillance resistance, metadata minimization, and operational security hardening. ## When to Use - Auditing privacy-sensitive applications - Reviewing journalist/activist threat models - Hardening communications platforms - Assessing metadata leakage in protocols and applications - Evaluating anonymous communication systems - Reviewing data retention and logging policies - Assessing exposure to lawful intercept and legal compulsion ## Threat Model Tiers Structure analysis by adversary capability. Each tier subsumes the capabilities of all lower tiers. | Tier | Adversary | Capabilities | |------|-----------|-------------| | **1** | Passive network observer | ISP, coffee shop WiFi, upstream AS. Sees DNS, IP flows, unencrypted traffic. | | **2** | Active network attacker | MITM, DNS manipulation, BGP hijack, certificate compromise via rogue CA. | | **3** | Platform-level adversary | Cloud provider, app store, OS vendor. Access to plaintext data at rest, push notification content, software update channel. | | **4** | State-level | Lawful intercept (CALEA), FISA orders, national security letters with gag orders, IMSI catchers (Stingray), device exploit vendors (NSO Group). | | **5** | Global passive adversary | Traffic analysis across jurisdictions, correlation attacks on anonymity networks, upstream cable taps (UPSTREAM/PRISM-class). | Always define the threat tier before beginning an audit. Controls adequate for Tier 1 are meaningless against Tier 4. ## Surveillance Surface Taxonomy ### Network Metadata - DNS queries (reveal browsing intent even with HTTPS) - TLS SNI field (reveals destination hostname in plaintext pre-ECH) - Connection timing and duration patterns - Packet sizes and inter-arrival times (traffic fingerprinting) - IP address correlation across sessions ### Application Metadata - Push notification payloads (visible to Apple/Google) - App store analytics and telemetry - Crash reports containing device state - Update check frequency and timing - OAuth token exchanges revealing service usage ### Device Fingerprinting - Browser fingerprint (canvas, WebGL, fonts, screen resolution) - Hardware identifiers (IMEI, MAC address, serial numbers) - Sensor data (accelerometer, gyroscope uniqueness) - Installed font and plugin enumeration - TLS client fingerprint (JA3/JA4) ### Location Tracking - GPS and GNSS precise positioning - Cell tower triangulation (passive, no user consent needed) - WiFi positioning (BSSID databases) - Bluetooth beacons and BLE scanning - IP geolocation databases ### Communications Metadata - Who-talks-to-whom social graph (contact chaining) - Timing and frequency of communication - Message size and duration patterns - Group membership inference - Presence and online status indicators ### Financial Tracking - Payment processor transaction logs - Blockchain analysis and address clustering - Loyalty program purchase correlation - ATM and POS location tracking - Subscription service usage patterns ## Audit Methodology 1. **Map data flows** — Diagram all metadata emission points from client to server to third party. Include DNS resolvers, CDNs, analytics, crash reporting, and push notification services. 2. **Assess encryption coverage** — Evaluate protection for data in transit (TLS 1.3, certificate pinning), at rest (full-disk encryption, per-record encryption), and in use (enclaves, MPC, FHE where applicable). 3. **Evaluate authentication without identification** — Can users authenticate to the service without revealing real-world identity? Review account creation flow, recovery mechanisms, and payment requirements. 4. **Review logging and data retention** — What identifiers are logged server-side? For how long? Under what legal jurisdiction? Can logs be compelled via subpoena, NSL, or FISA order? 5. **Test traffic analysis resistance** — Are encrypted messages padded to uniform size? Is timing randomized? Is cover traffic generated? Can an observer distinguish message types by size or pattern? 6. **Assess supply chain integrity** — Are builds reproducible? Are dependencies pinned and audited? Is the signing key air-gapped? Can users verify binary-to-source correspondence? 7. **Review jurisdiction and legal compulsion exposure** — Map server locations, corporate domicile, and applicable legal frameworks. Identify single points of legal compulsion (one subpoena reveals all user data). ## Code Review Patterns Look for these anti-patterns in privacy-sensitive codebases: ``` # FINDING: Unnecessary logging of user identifiers logger.info(f"Request from user {user_id} at {ip_address}") # FIX: Log only what is operationally necessary; use rotating pseudonyms # FINDING: Unpadded encrypted messages reveal content type encrypted = encrypt(message) # FIX: Pad all messages to fixed size buckets before encryption encrypted = encrypt(pad_to_bucket(message)) # FINDING: Timestamps with unnecessary precision created_at = datetime.utcnow() # microsecond precision # FIX: Round to reduce temporal fingerprinting created_at = datetime.utcnow().replace(minute=0, second=0, microsecond=0) # FINDING: Device identifiers transmitted to server analytics.send(device_id=get_hardware_id()) # FIX: Use unlinkable session tokens; never transmit hardware IDs # FINDING: DNS queries leaking browsing intent requests.get("https://sensitive-site.org/resource") # FIX: Enforce DNS-over-HTTPS/TLS; consider Tor for DNS resolution # FINDING: Push notification content visible to platform provider send_push(user, title="New message from Alice") # FIX: Send empty/tombstone push; fetch content via E2E encrypted channel # FINDING: Certificate pinning absent or bypassable session = requests.Session() # no pin validation # FIX: Pin leaf or intermediate cert; detect and alert on pin failure ``` ## Hardening Checklist - [ ] **Network anonymity** — Tor/onion routing for metadata-resistant connectivity - [ ] **E2E encrypted messaging** — Signal protocol or equivalent with forward secrecy - [ ] **Metadata-resistant protocols** — Sealed Sender, Private Information Retrieval, oblivious HTTP - [ ] **Encrypted DNS** — DNS-over-HTTPS or DNS-over-TLS with trusted resolver; ECH for SNI - [ ] **Reproducible builds** — Deterministic compilation; users can verify binary matches source - [ ] **Air-gapped signing** — Software release signing keys on offline hardware - [ ] **Memory-safe crypto** — Rust, Go, or formally verified C for cryptographic implementations - [ ] **Minimal logging** — Log only what is operationally essential; auto-expire within days - [ ] **Jurisdiction diversity** — Distribute infrastructure across non-cooperating legal jurisdictions - [ ] **Warrant canary** — Publish regular signed statements of non-compromise; absence signals compulsion - [ ] **Anonymous account creation** — No phone number, no email, no payment required - [ ] **Forward secrecy** — Compromise of long-term keys does not reveal past communications ## Related Skills - `static-security-analyzer` — Automated code scanning for security vulnerabilities - `webapp-testing` — Web application penetration testing methodology - `secure-workflow-guide` — Secure development lifecycle and CI/CD hardening