CENSORS
sy Syria
Synonyms: SY
2 papers on file
- 2016-al-saqaf-internet Internet Censorship Circumvention Tools: Escaping the Control of the Syrian Regime
- 2014-chaabane-censorship Censorship in the Wild: Analyzing Internet Filtering in Syria
27 findings tagged here
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The merged KIO-IODA dataset (Jan 2018–Aug 2021) documents 219 national-scale Internet shutdowns across 35 countries and 714 spontaneous outages across 150 countries; the 35 shutdown-affected countries collectively represent more than 1 billion estimated Internet users. Myanmar (53 IODA events), Syria (52), and Iraq (38) are the most frequently affected countries in the shutdown dataset.
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The 30 key ASes computed from globally popular sites also intercept over 90% of paths to country-specific popular sites in nine censorious nations (China, Venezuela, Russia, Syria, Bahrain, Pakistan, Saudi Arabia, Egypt, Iran), covering 93.3% of paths to the top-50 country-specific sites. The same key AS set remained stable across repeated experiments conducted four months apart, suggesting durability over time.
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Router-level mapping of the 30 key ASes reveals that 11,709 individual routers must be replaced with Decoy Routers (non-censorious ASes only), at a hardware cost exceeding $10.3 billion USD. Individual large ASes require hundreds to over 1,600 router replacements (e.g., AS3356 needs 576, AS209 Quest Communications needs 1,662). Even targeting the weakest adversary studied, Syria (containable by 3 ASes at AS level), requires 1,117 DRs.
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Never-once avoidance succeeds for 75% of source-destination pairs that do not already terminate in the US (a highly routing-central country) at δ=0.5, and for nearly all pairs avoiding less central countries. Russia is the hardest case at ~35% success (δ=0.5) due to proximity to the dense European node cluster. The median successful source-destination pair has over 1,000 valid DeTor circuits when avoiding the US and 500 when avoiding China.
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Default bridges — whose IP addresses are hardcoded in the Tor Browser Bundle — carry 91.4% of all bridge clients globally in April 2016, and 86.1% in Iran and 69.2% in Syria. Because these addresses are trivially obtainable from the Tor Browser Bundle configuration files, a censor can block the vast majority of bridge users in a country at any time.
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Four OR ports (443, 8443, 444, 9001) account for 82% of all active public bridge fingerprints as of April 2016, down from 95% in March 2013 but still concentrated. Scanning just three of these ports (443, 8443, 9001) is sufficient to deanonymize 71% of all active public bridges. Additionally, CollecTor's published per-bridge usage statistics allow a censor to rank bridges by client count per country and identify the highest-impact OR ports to scan next.
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Table 2 shows that with 50 decoy ASes, the most powerful practical routing attack on downstream-only systems (rewiring-I) impacts 93% of China's routes (22.4% unreachable, 70% re-routed), compared to only 18.2% total impact from RAD on traditional upstream designs. Table 3 shows that even for Syria, the rewiring-II attack with just 1 downstream-only decoy AS already impacts 81% of routes versus 1.5% for RAD on upstream systems.
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Syria's 2015 blocklist contained a disproportionately large share of software-related sites because censors applied indiscriminate TLD-based blocking of all .il (Israeli) domain names regardless of content, demonstrating that non-topic-based criteria (country-code TLD, ASN) can sweep in entirely unrelated infrastructure and are detectable only through anomaly spot-checks rather than content analysis.
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Internet connectivity is the primary determinant of RAD attack strength across nation-state censors: China (573 ASes, 858 ring ASes) achieves a censorship metric of 0.277 under profile T1, while Syria (4 ASes, 5 ring ASes) achieves only 0.101 with the same decoy budget. Venezuela, despite fewer total ASes than Saudi Arabia (44 vs. 107), achieves a higher censorship metric (0.210 vs. 0.197) owing to its disproportionately large ring AS count (835 vs. 176), confirming that ring AS count predicts RAD capability better than raw AS count.
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Analysis of two days of leaked censorship log files from Syria shows that 1.57% of the population accessed at least one censored site — a proportion the authors argue is far too large for a user-focused surveillance system to pursue individually. This implies that simply flagging all users who access censored content is not a feasible targeting strategy for surveillance.
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Four circumvention tool names were explicitly blocked as URL substrings with zero allowed requests passing through: hotspotshield (126,127 blocked), ultrareach (50,769), ultrasurf (31,483), and the generic keyword israel (48,119). All matching requests — including update checks and background pings — were denied at 0% pass-through rate.
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Skype.com (503,932 censored, 0 allowed) and live.com IM services were blocked with 100% denial rates at all times. During the August 3, 2011 protest events Skype accounted for up to 29.24% of all censored traffic; 9% of Skype requests were software update attempts, which were also denied, confirming content-agnostic domain-level blocking rather than content-selective filtering.
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Syria's Blue Coat proxies blocked any URL containing the string "proxy," generating 3,954,795 censored requests (53.61% of all policy-censored traffic in Dfull). The collateral damage was severe: Google Toolbar's /tbproxy/af/query API calls and Facebook social plugins (/plugins/like.php at 43.04% and /extern/login_status.php at 38.99% of facebook.com censored traffic) together account for over 80% of censored facebook.com requests, all denied with 0 allowed counterparts.
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Syrian censors used a custom Blue Coat URL-category to policy_redirect specific Facebook pages (Syrian.Revolution: 1,461 censored) while allowing 17.70M facebook.com requests overall — only 1.62M (8.4%) were censored. The URL-pattern matching was imprecise: www.facebook.com/Syrian.Revolution?ref=ts was blocked but the identical page with additional AJAX query parameters (__a=11&ajaxpipe=1) was not categorized as 'Blocked Site,' leaving some access through.
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Port 9001 (Tor) ranked third among all blocked ports in Syria, behind only ports 80 and 443. Proxy SG-48 was responsible for a disproportionate share of Tor censorship — blocking Tor traffic for multiple consecutive days — while other proxies in the same deployment did not, indicating per-proxy policy specialization or traffic steering of suspected circumvention flows to dedicated blocking infrastructure.
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The feasibility of the RAD attack scales sharply with the censor's network connectivity. Strategic placement of decoys in just 1% of ASes disconnects China from 18% of Internet destinations, Venezuela from 54%, and Syria from 87%. Countries with fewer controlled ASes and ring ASes have dramatically less routing flexibility and are far more vulnerable to even small decoy deployments.
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SkypeMorph and FreeWave both overlay a client-proxy communication model onto a peer-to-peer VoIP network; because Skype clients attempt direct peer contact before falling back to supernodes, initiating a call to a FreeWave proxy reveals its IP address directly to the caller, and proxy nodes accumulate user-to-bridge ratios that reached 8–12× in Syria/Iran and up to 120:1 in China (Figure 8), producing concentration signatures uncharacteristic of normal P2P call distributions. These architectural mismatches allow enumeration and fingerprinting attacks independent of traffic-content analysis.
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In four of five incidents (all except Syria), spam accounts were registered in temporally clustered blocks while legitimate accounts were not; in Russia and Mexico, multiple distinct registration bursts were observed. Across all five incidents, spam account usernames were automatically generated, with China'12 and Mexico accounts following a {name}{name}{number} pattern padded to exactly 15 characters (Twitter's maximum), making algorithmic reverse-engineering feasible.
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Across five political spam incidents, spam constituted 62–73% of all tweets in the Russia, China'12, and Mexico incidents, while Syria had only 6% spam. In the China'12 incident, 1,700 spam accounts (14% of all accounts) generated 600,000 spam tweets (73% of total), with 10 individual accounts each producing over 5,000 tweets before shutdown; in Mexico, 50 accounts sustained 1,000 spam tweets per day throughout the incident.
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Twitter's existing automated spam-filtering mechanisms caught only approximately 50% of politically motivated spam in the Russian parliamentary election incident, as reported by Thomas et al. (2012) and noted as the baseline for this study. Spammer behavior varied sufficiently across incidents (targeting strategy, URL usage, mention patterns, default-profile adoption) that supervised machine-learning classifiers trained on one incident are unlikely to generalize to others.
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As of March 2013, Tor is documented as blocked in China, Iran, Syria, Ethiopia, the UAE, and Kazakhstan. Blocking techniques range from simple IP address blacklisting to a sophisticated hybrid consisting of deep packet inspection (DPI) and active probing.
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BlueCoat's commercial DPI hardware/software, deployed in Syria, was confirmed capable of detecting and blocking Ultrasurf connections. BlueCoat logs recovered from Syria additionally exposed real Ultrasurf user behavior, including unproxied traffic leaking to non-Ultrasurf servers before and after bootstrapping completed.
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A warden can fingerprint the specific covert destination a Telex user is visiting by comparing observed latency distributions against a pre-built database of covert-destination latencies. With an intelligently filtered database of only 10 distributions (K-S inter-entry threshold 0.8), the AUC is 0.868, and with approximately 12 collected samples the false positive rate drops below 10%. Larger databases (size 50) degrade to AUC 0.537 due to distribution similarity, but threshold-based filtering restores substantial discriminative power.
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A routing-capable warden can enumerate over 90% of decoy-router-deploying ASes for deployments as large as 4,000 ASes using an intersection-based discovery attack: the warden probes many paths, accumulates a set of 'clean' ASes, and prunes candidate paths until a single 'tainted' AS remains. All evaluated wardens (China, Syria, Iran, Australia, France, Venezuela) achieved roughly equal detection success across all deployment sizes.
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Containment analysis shows that surrounding China with a 'ring' of decoy routers at AS-hop depth 1 requires covering 161 ASes; depth-2 expands by a factor of more than 23, becoming untenable, while depth-3 is slightly smaller but leaves the majority of the Internet reachable via clean paths. Cutting China off from at least half the Internet would require all 96 of the world's largest ISPs to deploy decoy routers at all exit points simultaneously.
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Under the Cirripede 'random ASes' deployment scenario — where 0.4%–1.0% of ASes deploy decoy routers — routing-capable wardens need only disconnect themselves from 0.85%–3.04% of the Internet to obtain clean (decoy-free) paths to all remaining destinations. Even at 10% Internet-wide deployment, wardens are cut off from only 7%–9% of non-participating ASes on average.
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A passive timing attack using the Kolmogorov-Smirnov test on connection latency distributions reliably distinguishes Telex users from honest hosts: K-S scores against the overt destination max out at 0.26, while scores against covert destinations (even those within 10 ms of the Telex station) range from 0.3–1.0 with a median of 0.7 for nearby servers and 1.0 for Alexa top-100 sites. The attack is effective even for clients 50–250 ms from the Telex station, with no K-S score below 0.26 observed across 40 PlanetLab hosts.