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