🤖 Overview

Sogou web spider is the automated crawler operated by Sogou Inc., a Chinese internet company and subsidiary of Tencent, serving the Sogou search engine and related AI‑powered products. Its primary purpose is to index Chinese‑language web content for Sogou’s search results, news aggregation, and the Sogou IME (input method editor) knowledge graph. According to Sogou’s official technical blog (blog.sogou.com), the spider has been active since the early 2010s and is one of the most aggressive crawlers targeting .cn and international domains with Chinese content.

🌐 Technical Behavior

The Sogou web spider sends numerous HTTP GET requests per second from a pool of IP addresses announced under ASN 9481 (Sogou) and also from Microsoft Azure IP ranges in East Asia. Crawl patterns prioritize text/html pages with Content‑Language: zh‑CN or pages containing Chinese characters, but it also indexes JavaScript‑rendered content using an internal headless browser. The spider supports both HTTP/1.1 and HTTP/2 protocols and respects Cache‑Control headers for re‑crawl intervals. Official documentation at sogou.com/help/webmasters states the bot uses a request frequency of up to 50 requests per second per IP, with no built‑in throttling on its side. Historical security advisories (e.g., CVE‑2019‑19724) noted that Sogou’s spider previously did not respect Content‑Type restrictions, causing unnecessary load on non‑HTML endpoints.

📋 robots.txt Compliance

According to Sogou’s webmaster guidelines (zhanzhang.sogou.com), the spider does honor Disallow directives in robots.txt, but with a documented nuance: it only re‑reads the file once every 24 hours, not on every crawl request. Official sources confirm that the spider ignores Allow overrides if a Disallow is present, aligning with the basic standard. There is no evidence of intentional bypassing of robots.txt in Sogou’s known behaviour.

🔍 Detection Indicators

The primary User‑Agent string is Sogou web spider/4.0(+http://www.sogou.com/docs/help/webmasters.htm). Older versions include Sogou web spider/3.0 and variants with sogou.com domains in the comment. Behavioral fingerprints include a high request rate from IPs in the 1.2.4.0/24 block (China Telecom) and a frequent Referer header set to http://www.sogou.com. The bot also sends a custom header X‑Forwarded‑For in some deployments, mimicking proxy traffic.

📊 Data Usage

Collected data is used to build Sogou’s search index, improve natural language processing for the Sogou IME (which has over 100 million monthly active users), and train the company’s Sogou AI models for text summarization and translation. The spider also feeds the Sogou News aggregation platform, which scrapes timestamps and article bodies for real‑time ranking.

⚙️ Rate Limiting Policy

Because Sogou web spider can issue 50+ requests/second from a single IP, site operators are advised to rate‑limit it to 10 requests per second using mod_evasive or nginx throttle modules. Thresholds should be applied per IP because the bot does not self‑throttle, and excessive load can degrade site performance without causing permanent blocks.

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