A deep dive into the TCP layer of Voidly's censorship detection: SYN-ACK timing, RST injection detection with a 15ms threshold, null-routing vs. RST as two distinct censorship mechanisms, the TcpResult struct, dual-IP probing to identify RST source, and how TCP evidence maps to the anomaly classifier's interference classes.
October 2025
5 dated technical articles. These pages record the methods and claims as published; follow each article's source links and update notes for its current scope.
How Voidly uses a distributed control server network to distinguish genuine censorship from network errors, CDN split-horizon DNS, and misconfigured sites — DNS, TCP, TLS, and HTTP comparison methodology, and why a single control is not enough.
Censorship and information control · Engineering and infrastructure
A technical deep-dive on how Voidly detects bandwidth throttling — the hardest interference class to classify. Covers the TimingFeatures Rust struct, TTFB z-score computation against control measurements, body truncation and mid-transfer RST signals, the congestion vs. deliberate-throttling calibration problem, cross-probe corroboration scoring, and country patterns from Russia TSPU, Iran ARRS, India, and China.
Censorship and information control · Engineering and infrastructure
How Voidly monitors 37+ probe nodes: heartbeat system (60s cadence, separate transport), DEGRADED/OFFLINE state machine, measurement quality scoring, ASN coverage SLOs for 200 countries, flapping detection capping confidence at CORROBORATED, automated replacement from standby operator waitlist, and the classify_offline_cause() algorithm distinguishing probe failure from ISP-level censorship.
Censorship and information control · Engineering and infrastructure
How Voidly probes identify DNS injection and manipulation in censored networks — comparison against three control resolvers, four weighted detection signals (IP divergence, TTL anomaly, source IP divergence, response timing), per-country injection rates (China 94%, Iran 61%, Russia 12%), CAP_NET_RAW privilege handling, anycast false-positive calibration from 4.2% to 0.8%, and integration with the DnsTestResult confidence score.
Censorship and information control · Engineering and infrastructure