All confirmed URL filtering deployments—McAfee SmartFilter in UAE and Netsweeper in Yemen, UAE, and Qatar—block content across at minimum six of seven tested human-rights-sensitive categories: media freedom, human rights, political reform, LGBT, religious criticism, and minority groups/religions. Netsweeper in both Qatar (Ooredoo) and UAE (Du) blocks all seven categories. This content is protected under Article 19 of the Universal Declaration of Human Rights.

In YemenNet (AS 12486), URL filtering was observed to be intermittently offline: proxy URLs accessible in one test run were blocked in others and vice versa. A prior ONI measurement found a Yemeni ISP running Websense whose filtering ceased entirely when concurrent user count exceeded the product's license capacity. This inconsistency required larger URL test sets and repeated measurement runs to establish blocking with high confidence.

§4.4 evaluation

In every ISP where URL filtering was empirically confirmed, the 'proxy anonymizer' category was actively blocked. Netsweeper blocked 6/6 submitted proxy domains in YemenNet (AS 12486), 5/6 in Du UAE (AS 15802), and 6/6 in Ooredoo Qatar (AS 42298); McAfee SmartFilter blocked 5/5 anonymizer-category submissions in Etisalat UAE (AS 5384). Blue Coat in UAE and Qatar did not confirm—Etisalat appears to use SmartFilter for URL filtering atop a Blue Coat proxy appliance for traffic management.

§4.3–4.5, Table 3 detection

URL filtering appliances are frequently misconfigured to be externally visible on the global Internet, enabling passive identification via Shodan keyword searches on product-specific HTTP headers and management console paths (e.g., 'cfru=' for Blue Coat, '8080/webadmin/' for Netsweeper). This technique discovered previously unknown installations in Finland, Sweden, Philippines, Thailand, Taiwan, Argentina, and Chile, as well as large U.S. ISPs including AT&T, Verizon, Bell South, Comcast, and Sprint.

§3, Figure 1 evaluation

The paper presents a repeatable method for confirming which specific URL filtering product is used for censorship: create test domains under researcher control, submit a subset to the vendor's public URL categorization interface, then retest within 3–5 days to observe whether submitted domains become blocked. This technique confirmed McAfee SmartFilter in UAE (Etisalat, AS 5384) and Saudi Arabia (Bayanat Al-Oula AS 48237, Nournet AS 29684), and Netsweeper in Qatar (Ooredoo AS 42298), UAE (Du AS 15802), and Yemen (YemenNet AS 12486).

§4.2, Table 3 evaluation

During the June 2025 shutdown, Iranian authorities blocked international One-Time Password (OTP) SMS delivery, preventing new sign-ins to foreign secure-messaging platforms and VPN services. This forced users toward government-approved domestic platforms that lack security and privacy protections. The blockade of OTPs effectively weaponized account-recovery flows as a secondary shutdown layer, disproportionately affecting users who needed to activate new circumvention tools during the crisis.

2025-iran-shutdown-measurement §Human Rights Implications port-blockingdpikeyword-filtering

Simple character-level perturbations (English) and homophone substitutions (Chinese), combined with LLM instruction-following prompts directing the model to use word substitutions in its output, successfully bypassed all input and output filters for all 41 input-blocked and 197 output-blocked queries across five major Chinese LLM services (Baidu-Chat, DeepSeek, Doubao, Kimi, Qwen). Every input-blocked query contained at least one keyword combination that alone triggered the filter, confirming keyword-matching rather than semantic classification.

2026-ablove-characterizing §VII-D keyword-filtering

Cross-national experiments conducted from Singapore, South Korea, and Taiwan during February 19–24, 2025 found no variance in blocking implementations, event syntax, or server infrastructure across all five Chinese LLM services. Input blocking was enacted identically in all three international locations, and services connected to the exact same server IP addresses globally — Kimi and Baidu-Chat connected to identical IPs and DeepSeek to the same two addresses across all tested locations.

2026-ablove-characterizing §VIII-A keyword-filtering

Input blocking in Chinese LLM services (DeepSeek, Qwen, Kimi, Doubao) is overwhelmingly consistent: all four services persistently block the exact same queries across all 5 measurement samples in both Simplified and Traditional Chinese. Output blocking is far less consistent, with only 29 out of 349 output-blocked queries blocked across all 5 samples. Baidu-Chat is exceptional: it performs almost no input blocking but instead relies heavily on post-search and output blocking (78.6% of blocks are output-phase).

2026-ablove-characterizing §VI-B keyword-filteringdpi

DeepSeek, Kimi, and Doubao all transmit analytics logs to the same Autonomous System (AS24429, Zhejiang Taobao Network Co., Ltd., a ByteDance/Volcengine subsidiary), with one monitoring endpoint IP directly overlapping between DeepSeek and Doubao. Additionally, all four non-Qwen services maintain connections with servers physically located in China throughout the chat session, transmitting user IDs, session IDs, viewport data, language preferences, and in Baidu-Chat's case, the full query text via URL-encoded CAPTCHA requests.

2026-ablove-characterizing §VI-D keyword-filtering

All five Chinese LLM services transmit partial or complete responses to the client machine even when output blocking is triggered, representing a major information leak. For DeepSeek and Qwen, truncated blocked responses are on average close in token length to full successful responses. For Baidu-Chat, the complete response is transmitted to the client but only partially rendered in the browser UI, with only a word or two visible on screen.

2026-ablove-characterizing §VI-C keyword-filtering