Understanding Bots/Web Crawlers/Spiders

Modified on Fri, 25 Oct at 2:59 PM

What are bots/web crawlers/spiders?

A web crawler (also known as a spider, bot, or web robot) is an automated program that visits web pages on the internet, analyzes their content, and indexes them for search engines or other services. Bots access websites by sending requests, similar to how a human user would, but they can do this on a much larger scale and faster pace.

Bots exist to automate tasks that would be time-consuming or impossible for humans to do manually. They help with things like indexing websites for search engines, gathering data, automating customer service through chatbots, and monitoring online activity. While many bots are useful and improve efficiency, some are designed for malicious purposes, such as spamming, scraping content, or attempting cyberattacks. Overall, bots exist to streamline processes, both for beneficial and harmful purposes, depending on how they are programmed.

Examples:

Googlebot: Google’s web crawler that indexes pages for Google Search.
AhrefsBot: Ahrefs’ bot, which is used primarily for SEO data collection and link analysis.
Bingbot: Microsoft's bot that indexes pages for Bing Search.
Other Bots: Various other companies (e.g., SEMrushBot, YandexBot) have their own crawlers for collecting data.

How do bots/web crawlers/spiders work?

Discovery: Crawlers start by visiting a list of known URLs, often referred to as a "seed list." These could be URLs that were manually added or that the bot has discovered through previous crawls.
Crawling: Once on a page, the bot reads the entire content of the page, including text, images, links, metadata, and more. The crawler also follows internal and external links on the page to discover new content. This allows the bot to continuously "crawl" through the web, discovering more and more pages.
Indexing: The crawler takes the information from the pages it visits and sends it to its corresponding database for indexing. Indexing is the process of analyzing and storing the page’s content so that it can be quickly retrieved during searches.
Frequency: Web crawlers visit pages at different frequencies, based on factors like the popularity of the site, how often it updates, or the priority it has in the crawler’s system.
Respecting Robots.txt: Most bots follow the instructions in a site's robots.txt file, which is a set of rules that tell bots which pages they can or cannot crawl. This file can be used to block certain parts of a website from being crawled by bots.
Data Collection: Each bot collects different types of data depending on its purpose:
- Googlebot collects data for indexing pages in Google Search.
- AhrefsBot collects data like backlinks, SEO metrics, and site health for its SEO tools.
- Other bots may collect analytics data, performance information, or monitor specific content.

Can bots visit my site more than once?

Yes, bots can visit your site multiple times. Some bots, like search engine crawlers, regularly revisit websites to check for updates. Other bots may visit your site repeatedly for different reasons, like scraping data or spamming.

How does Pathmonk detect bots?

At Pathmonk, we understand that protecting your website from bots is crucial for maintaining a smooth user experience and safeguarding your data. Bots can be both helpful (e.g., search engine crawlers) and harmful (e.g., malicious scraping, spamming, or trying to hack your website). Therefore, it’s essential to distinguish between legitimate visitors and potentially harmful bots. Below, we outline key techniques to detect bots effectively and ensure your website functions optimally while staying secure.

1. Behavioral Analysis
One of the most effective ways to detect bots is by analyzing user behavior. Human users tend to navigate websites more organically and unpredictably, while bots often exhibit patterns that are mechanical or repetitive.

Mouse Movements and Clicks: Real users move their mouse and interact with elements in varying ways, but bots often click or interact with links programmatically without typical human behavior like hovering or smooth scrolling. Monitoring for erratic or overly consistent patterns in clicks and mouse movements is a telltale sign of bot activity.
Time on Page and Session Duration: Bots tend to spend either too little or too much time on a page, typically moving very quickly or staying in one place for an unusually long period. Short bursts of activity without interaction, or pages being loaded in a fraction of a second, could indicate automation rather than a human browsing experience.

2. Request Frequency and Velocity
Bot detection can also be performed by analyzing the frequency and velocity of requests made to your server. Human visitors generally browse at a slower pace, whereas bots can make hundreds or thousands of requests in a very short period.

Rate Limiting: Implementing rate limits on requests per user session can help detect bots. Bots that attempt to access your website too quickly, especially in a short time window, can be flagged as suspicious and either throttled or blocked.
Unusual Traffic Spikes: A sudden and unusual increase in traffic from specific IP addresses, regions, or user-agents could indicate bot attacks, such as Distributed Denial of Service (DDoS) or brute force login attempts. Setting thresholds for request volumes can help you identify this bot activity.

3. Device Fingerprinting and IP Reputation
Device fingerprinting helps identify unique visitors by collecting details about their browser, operating system, screen resolution, installed plugins, and other attributes. Even if a bot changes IP addresses, device fingerprints can help you track them across sessions.

Browser and Header Anomalies: Many bots have incomplete or abnormal browser headers because they do not replicate human browsers perfectly. Comparing headers such as User-Agent, Accept-Language, or Referer to known legitimate values can reveal discrepancies indicating bot behavior.
IP and Proxy Detection: Bots often use proxy servers or VPNs to disguise their true location. You can monitor for IP addresses linked to known bot networks or data centers. Using IP reputation databases can flag requests from suspicious sources or regions.

4. User-Agent and Referrer Analysis
Bots often have distinct user-agent strings or referrer data, either using well-known bot signatures or generic, unusual strings that differ from real browser user-agents.

Whitelist and Blacklist User-Agents: By maintaining a whitelist of known legitimate user-agents (e.g., Googlebot, Bingbot), you can allow trusted crawlers while blocking user-agents that are known to be associated with malicious or unwanted bots.
Referrer Header Inspection: Bots may use improper or unusual referrer headers that don’t match real traffic patterns. Validating and inspecting these headers can help filter out non-human traffic.

5. JavaScript and Cookie Challenges
Many bots operate without fully supporting JavaScript or cookies, which are commonly used by websites to enhance user experience and track behavior.

JavaScript Challenges: Presenting a JavaScript challenge (like requiring execution of specific JS functions) can identify bots that cannot run JavaScript. These challenges can be invisible to users but will prevent bots from interacting with your website.
Cookie Challenges: Some bots cannot store cookies or handle complex session management. Implementing challenges based on cookie storage or manipulating cookies can differentiate real users from bots.

Why does Pathmonk detect and show bots?

Understanding your crawler traffic through Pathmonk’s transparent bot detection is key to maintaining an efficient, secure, and optimized website.

Improved Data Accuracy: Without knowing the extent of bot traffic, your analytics data can be skewed, leading to misinterpretation of user behavior. Identifying and filtering bot traffic ensures that your metrics reflect real human interactions.
SEO Optimization: Some bots, like search engine crawlers, are beneficial for SEO as they help index your content. However, knowing which crawlers visit frequently allows you to prioritize important pages and prevent less important ones from being over-indexed.
Prevent Performance Issues: Bots that crawl your site excessively can slow down load times for real users. By understanding which bots are visiting, you can take steps to reduce their impact, ensuring a better user experience.
Security Monitoring: Being aware of malicious or unknown bots helps safeguard your site. You can react quickly if you notice bots attempting to exploit weaknesses, enabling you to enhance your site’s security.

What should you do if your website is receiving a lot of bot traffic?

If you receive a lot of crawler traffic on your site, there are several actions you can take, and knowing about these crawlers is crucial for several reasons:

Update your Robots.txt file: By modifying your robots.txt file, you can control which crawlers have access to specific parts of your website. For example, you can block certain bots from crawling non-essential or sensitive pages, reducing unnecessary server load.
Use Bot Management Tools: Some tools, including firewalls and security services, allow you to filter, block, or rate-limit traffic from bots. You can set up rules to prevent unwanted or harmful bots from consuming your bandwidth.
Analyze Bot Behavior: Pathmonk provides transparency by showing which bots are arriving, allowing you to analyze their behavior. If certain bots are indexing your content aggressively or scraping sensitive data, you can take targeted actions to block them or redirect them.
Optimize Server Resources: Heavy bot traffic can strain your server resources. By knowing which bots are frequenting your site, you can take steps like caching pages more effectively or adjusting server settings to handle traffic more efficiently.
Identify Potential Security Risks: Some crawlers are malicious, aiming to exploit vulnerabilities. By monitoring the bots visiting your site, you can detect unusual patterns or malicious activity early, preventing possible cyberattacks.