Why relying on complex subdomain names won’t stop bots from finding your site

Many website owners may believe that creating complex, obscure subdomain names will help hide sensitive parts of their web infrastructure from bots and malicious actors. This practice, often referred to as “security through obscurity,” assumes that the more intricate and hard-to-guess a subdomain name is, the less likely it will be discovered. However, in reality, this approach is far from effective, and relying solely on complex subdomain names to secure your site can leave you vulnerable to various threats.

Here are several reasons why using complicated subdomain names won’t protect you from bots:

1. Bots Use Comprehensive Scanning Techniques

Modern bots are equipped with sophisticated tools that do much more than simply guess or brute-force subdomains. They employ techniques like DNS brute-forcing, where they use wordlists of common and uncommon subdomain names to discover hidden parts of a website. This means that even a highly complex subdomain can be found if it matches a pattern or is similar to other subdomains that are often used.

Additionally, bots frequently leverage publicly available Certificate Transparency (CT) logs, which list SSL certificates issued for all subdomains of a domain. Services like crt.sh provide easy access to these logs, making it possible to find any subdomain that has been issued an SSL certificate, regardless of its complexity. If your subdomain uses HTTPS, it’s very likely that bots can find it through these logs.

2. Search Engines and Indexing Bots

Search engines like Google and Bing index entire websites, including subdomains, as part of their crawling processes. Even if your subdomain is not explicitly linked from your main website, crawlers may still find it through direct DNS lookups or through links that are inadvertently left on the internet (for example, in forum posts or social media mentions).

Once a search engine indexes your subdomain, it becomes publicly accessible through search results, making it easy for bots and malicious actors to find. Bots frequently scrape search engine data to identify hidden or less-visible areas of websites, and they can easily stumble upon complex subdomains this way.

3. Public Leaks and Misconfigurations

No matter how obscure your subdomain is, it’s only as secure as your overall infrastructure. Human error or misconfigurations can lead to accidental exposure. For example, subdomains can be accidentally revealed through:

Public logs or monitoring tools: Developers or administrators may inadvertently leave subdomain details in publicly accessible logs or monitoring dashboards.

Third-party services: Many online tools and services (such as analytics platforms, CDN providers, or marketing tools) may list or expose subdomains as part of their reporting or API data.

Content delivery networks (CDNs): If your website is using a CDN, its infrastructure might expose subdomains through reverse DNS lookups or other methods.

Once any of these misconfigurations occur, bots have an easier time discovering even the most complex subdomain.

4. Subdomain Enumeration Tools

There are a variety of publicly available tools that specialize in subdomain enumeration. Tools like Sublist3r, Amass, and MassDNS are designed to scan DNS records and use techniques such as brute-forcing, OSINT (Open Source Intelligence), and leveraging public data to enumerate subdomains. These tools often rely on massive wordlists or use wildcard DNS lookups, enabling them to discover complex subdomains relatively easily.

Even if your subdomain is obscure, it might still be discovered by these tools simply by existing in the DNS space.

5. Security Through Obscurity is Not True Security

The fundamental issue with relying on complex subdomain names is that obscurity is not a substitute for security. While it might make it marginally harder for casual attackers to find certain parts of your infrastructure, determined attackers and bots equipped with modern techniques will still be able to locate your subdomains.

The philosophy of “security through obscurity” gives a false sense of security. If a subdomain holds sensitive information or critical infrastructure, it should be protected by proper security measures such as:

Authentication and authorization: Always require proper user credentials and permissions to access sensitive areas of your site.

IP whitelisting: Restrict access to sensitive subdomains to specific IP addresses or ranges that you control.

Firewall and rate-limiting: Use a Web Application Firewall (WAF) and rate-limiting to prevent bots from enumerating or attacking your infrastructure.

HTTPS and encryption: Secure subdomains with SSL certificates and ensure encrypted communication is enforced to protect against eavesdropping.

6. The Importance of Proactive Security Measures

Ultimately, preventing unauthorized access to sensitive subdomains requires active security measures, not passive reliance on obscure names. Effective security strategies should involve monitoring traffic, detecting suspicious behavior, and using robust security protocols.

Moreover, auditing your infrastructure regularly and reviewing DNS configurations can help you identify any unnecessary subdomains that may expose potential attack vectors. Implementing strong security practices across your website’s architecture, rather than relying on the complexity of subdomain names, is key to protecting your web assets from bots and malicious actors.

Conclusion

While using complex subdomain names might seem like a quick fix to avoid bot discovery, it is by no means a reliable security measure. Modern bots use a wide array of techniques, from DNS brute-forcing to public data mining, to discover subdomains, no matter how obscure they may be. Instead of relying on “security through obscurity,” website owners should implement robust security measures such as authentication, encryption, and monitoring to truly safeguard their web infrastructure.

In short, don’t expect a complex subdomain name to shield your site from bots. Proper security practices will always be your best line of defense.