Web crawlers, also known as spiders or data crawlers, are automated bots that systematically browse the internet, collecting data from websites. They play a critical role in how search engines index web pages and  how they deliver content. Like most things on the web, some are good but others can do a lot of harm to your website’s performance, security, and bottom line.

Let’s take a closer look at web crawlers  – what they are, how they work, why they can be problematic, and how you can prevent them from wreaking havoc on your website.

What Is a Web Crawler?

A web crawler (or data crawler) is a bot that scans and collects information from websites. These bots are often used by search engines to index web content, which allows users to use search queries to find the content they need. This type of crawler is beneficial, but not all crawlers are created equal.

For example, some crawlers exist solely to scrape content, steal data, or flood your server with unnecessary requests. These activities can negatively impact your website’s performance and security.

How Does a Web Crawler Work?

A web crawler typically starts with a list of initial URLs, known as seed URLs. It visits these pages, downloads the content, and then follows any links it finds on those pages to discover more web pages. As the crawler continues to explore, it indexes the content, making it easier for search engines to display it in their results.

Legitimate crawlers use an user-agent string – a small piece of text in the request header that tells the server which bot is visiting – as an identifier. Malicious crawlers, however, may spoof this information or not provide it at all.

What Is Crawler Activity?

Crawler activity refers to the actions these bots perform as they browse your site. This can include visiting multiple pages, following links, and downloading content for indexing or data collection. While this is helpful for search engines, if there’s a lot of crawler activity it can result in a heavy load on your server and increase security risks.

The only way to track this activity is through server logs monitoring. If you identify a particular bot making too many requests, you can block or limit its activity.

How to Check a Crawler

By looking at a crawler’s user-agent string in your server logs, you can determine good versus bad crawlers. Legitimate crawlers will identify themselves in the string. Malicious crawlers may try to hide it through fake strings. That’s why it’s important to use bot detection tools that analyze traffic behavior to identify unwanted or harmful bots.

Why Are Web Crawlers a Problem?

While search engine crawlers help with SEO and content discovery, other bots can become a major issue for hosting providers. Here’s why:

1. Server Overload: Malicious crawlers can overload your server, reducing performance for legitimate users. This unnecessary traffic can eat into your server’s bandwidth and slow down your website.
2. Data Scraping: Bad actors may use crawlers to steal content, pricing data, or even sensitive user information, leading to data breaches.
3. Security Vulnerabilities: Malicious bots may also try to exploit vulnerabilities in your website, such as unpatched software or weak login pages, opening the door to potential security attacks.
4. Skewed Analytics: Unwanted bots can distort your web analytics by inflating traffic numbers, making it difficult to accurately assess real user behavior and engagement.

How to Prevent Unwanted Web Crawlers

You want to let in good bots, like those from search engines, while blocking harmful ones. Here are some strategies to manage crawler activity effectively:

1. Robots.txt File

The robots.txt file is the first line of defense against unwanted crawlers. It tells web crawlers which pages or sections of your site they are allowed to visit and which ones they should avoid. For example:

txt

Copy code

User-agent: *

Disallow: /private-section/

This code tells all bots to avoid the “/private-section/” directory. However, keep in mind that malicious bots often ignore robots.txt rules.

2. BotGuard for Real-Time Detection

Using a dedicated bot protection solution can help you monitor and block malicious bots in real time. Trusted bot protection solutions use advanced AI and machine learning to analyze traffic patterns, detect unwanted bots, and prevent them from consuming resources or scraping sensitive data.

3. CAPTCHAs

CAPTCHAs are useful for stopping bots from abusing forms or registration pages. By requiring users to solve a puzzle or complete a task, you can filter out a significant portion of automated bot traffic.

4. IP Blocking and Rate Limiting

Blocking suspicious IP addresses and applying rate limits to prevent too many requests from a single source can also mitigate bot activity. This is particularly helpful when dealing with brute-force bots or scrapers that hammer your server with requests.

5. User-Agent Filtering

You can configure your server to allow or block traffic based on the bot’s user-agent string. This method is helpful for controlling which crawlers can access your site, but you must be cautious of bots using fake user-agent strings to bypass this measure.

6. JavaScript Challenges

Some bots are unable to process JavaScript, so adding a JavaScript challenge can prevent them from accessing your site’s content.

Conclusion

Web crawlers are an essential part of how the web functions, but they can also create problems for hosting providers. Managing crawler activity is critical to maintaining your server’s performance, security, and data integrity. By implementing a bot detection solution like BotGuard, you can allow helpful bots to access your site while keeping harmful or unnecessary ones at bay. This proactive approach not only optimizes your website’s performance but also protects your business and your website.

Photo by Ant Rozetsky on Unsplash