Published on 2025-08-07T06:18:08Z

SurdotlyBot

SurdotlyBot is a security-focused web crawler operated by the safe browsing service Sur.ly. Its purpose is to analyze the links on a website to identify and validate potential security threats, such as malware or phishing attempts. It does not index content for search but rather serves to build Sur.ly's safety database, which helps protect internet users from malicious links.

What is SurdotlyBot?

SurdotlyBot is a specialized web crawler from the safe browsing service Sur.ly. It functions as a security-oriented crawler, analyzing links on websites to identify potential threats. The bot identifies itself in server logs with a user-agent string like Mozilla/5.0 (compatible; SurdotlyBot/1.0; +http://sur.ly/bot.html). Unlike general-purpose crawlers, SurdotlyBot does not execute JavaScript or render pages fully; its focus is specifically on link analysis rather than content scraping.

Why is SurdotlyBot crawling my site?

SurdotlyBot is visiting your website to validate its links and assess their safety. It is examining the outbound links on your pages to determine if they lead to legitimate destinations or to potentially harmful content. It is not interested in your page content itself but in the network of connections your site makes to other domains. Its crawl frequency is generally conservative, and its presence may be more common on sites with many external links.

What is the purpose of SurdotlyBot?

The purpose of SurdotlyBot is to support Sur.ly's safe browsing services through preemptive threat detection. Its functions include malware detection, phishing prevention, and content authenticity verification. The bot's activity helps build Sur.ly's safety database, which in turn helps protect users from malicious websites. For website owners, the crawling can indirectly benefit your site's reputation if your links are classified as safe. However, the bot does not directly contribute to your search engine visibility.

How do I block SurdotlyBot?

To prevent SurdotlyBot from analyzing your site's links, you can add a disallow rule to your robots.txt file. This is the standard method for managing crawler access.

To block this bot, add the following lines to your robots.txt file:

User-agent: SurdotlyBot
Disallow: /

How to verify the authenticity of the user-agent operated by Sur.ly?

Reverse IP lookup technique

To verify user-agent authenticity, you can use host linux command two times with the IP address of the requester.
  1. > host IPAddressOfRequest
    This command returns the reverse lookup hostname (e.g., 4.4.8.8.in-addr.arpa.). 
  2. > host ReverseDNSFromTheOutputOfFirstRequest
If the output matches the original IP address and the domain is associated with a trusted operator (e.g., Sur.ly), the user-agent can be considered legitimate.

IP list lookup technique

Some operators provide a public list of IP addresses used by their crawlers. This list can be cross-referenced to verify a user-agent's authenticity. However, both operators and website owners may find it challenging to maintain an up-to-date list, so use this method with caution and in conjunction with other verification techniques.