With the wide application and increasing demand for network data, crawlers have become a common data acquisition tool. However, many websites are wary of the use of crawlers, because too frequent crawling behavior can put pressure on the website and even threaten the security of their data and normal operations. As a result, websites have adopted various methods to identify the behavior of crawler data collection in order to implement access restrictions or other measures. This paper will introduce the common methods and principles of website identification crawler data collection.
1. IP detection:
IP detection is a commonly used method to identify crawler data collection by monitoring the user's IP access speed and frequency to determine whether it is crawler behavior. When the same IP sends a large number of requests in a short period of time, exceeding the threshold set by the website, the website will flag it as abnormal behavior and take appropriate measures to restrict access to the IP, thereby preventing the crawler from continuing to obtain data. In order to avoid IP detection, crawlers adopt the strategy of using proxy IP to reduce the risk of detection by switching a large number of IP addresses, so as to capture public data smoothly.
2. Verification code detection:
Captcha detection is another common method of data acquisition for website identification crawlers, limiting overly frequent access by requiring users to enter a captCHA. A CAPtCHA is an authentication measure in the form of a graphic or text designed to confirm that a visitor is a real user and not an automated crawler. However, with the development of technology, modern crawlers have been able to use techniques such as optical character recognition (OCR) to crack general captCHA, thus bypassing the verification mechanisms of websites. In order to cope with this situation, websites continue to strengthen the difficulty of captCHA, using more complex forms, such as sliding captcha, image captcha and so on. 3. Request header detection:
Crawlers' requests often lack characteristics similar to those of real users, and websites can tell if they are crawlers by detecting the information in the request header. The request header contains information about the source of the request, the user agent, and so on, which the website can use to determine whether it is crawling behavior.
4. Cookie detection:
Cookie detection is another common method of website identification crawler data collection, by detecting visitors' Cookies to identify whether they are real users. Cookies are small text files that websites store on a user's computer to track the user's access and behavior, including login status, preferences and other information. When the user visits the website, the browser will send the corresponding cookie information to the website so that the website can identify the user and provide personalized services.
However, for crawlers, they usually do not support or fail to properly handle Cookies because crawlers often do not have the same functionality as browsers. Due to the lack of cookie information, the website will assume that these visitors may be crawlers, and take measures to restrict access to prevent crawlers from continuing to grab data.
To sum up, in order to protect the normal operation of the website and data security, the website has adopted a variety of ways to identify the crawler data collection behavior. Crawler users need to pay attention to these identification methods when collecting data, and take corresponding countermeasures, such as using proxy IP, processing verification codes, etc., to ensure the smooth progress of data collection. At the same time, crawler users should abide by the rules and use policies of the website, respect the data services of the website, and jointly maintain the healthy development of the Internet ecology.