Open Source Intelligence: How to investigate domain names

If an individual or organization owns a website, you should know how to access information about that website. The investigation may reveal the operating system used, software version, personal contact information, etc. It is recommended to investigate without "touching" the target's environment, a technique called passive reconnaissance - which involves using a footprint of tools and resources that can help obtain more information about the target without having to interact with it directly. Below I describe methods for obtaining information while remaining hidden.

Google Dorks

Google Dorks is a passive information gathering method that was already mentioned above. Here I’m going to show what queries might be useful during domain investigation.

· — limits search to a particular website or domain.

· filetype:DOC — returns DOC files or other specified types, such as PDF, XLS and INI. Multiple file types can be searched for simultaneously by separating extensions with “|”.

· intext:word1 — search for pages & websites that contain the specific word that you are searching.

· allintext: word1 word2 word3 — search for all the given words in a page or website.

· — will list web pages that are “similar” to a specified web page.

· site:* — show all subdomains. Asterisk acts as a substitute for a whole word or words in search queries.


Whois provides information about the registered user or assignee of an Internet resource, such as a domain name, IP address block, or autonomous system. There are many Whois resources, and these are good ones: and

Reverse Whois

Reverse Whois gives you a list of domains that have the same organization name or email address in their Whois record. For example, if you are investigating a company with the name “John Doe Inc.” you can see all the other domains registered under the “John Doe Inc.” One of my favorite websites is as it has an extensive toolkit, including reverse whois lookups.

Same IP

Often discovering which site is running on the same server as the target site will reveal valuable information. For example, you may find subdomains or development sites. Often, the service provider hosting this site is also responsible for other services - use and to check.

Passive DNS

Using only DNS records, you can see which IP resolves to a name or which name resolves to an IP. Sometimes this is not enough, and this is where passive DNS records come in handy. They allow checking all names that resolved to the IP under study, so you can build a useful resolution history. My favorite product is RiskIQ Community Edition because it provides information beyond just passive DNS. VirusTotal or SecurityTrails can also be used for this purpose.

Reputation, malware and referrals analysis

Reputation is important to know who you are dealing with and whether the site is trustworthy. If there is any doubt, a malicious activity check using a free online tool may save you the trouble of opening the site in a VM or performing other preventive measures. The recommended analysis is a search for internal and external HTML links. While testing alone will not provide you with accurate results, it is still one of the methods that can show you connected domains.

· - Analyzes website traffic (users, page views) and estimates how much revenue it can generate through advertising.

· - Analyzes website traffic and competitors, shows what they are doing better, and provides suggestions for SEO improvements.

· - Analytical tool that provides in-depth information about website or mobile rankings, performance, traffic sources, etc. Most importantly, it performs referral analysis.

· - Scans websites for known malware, blacklist status, website errors and outdated software.

· - Provides free malware scanning and comprehensive reports including malicious files, suspicious files, blacklist status and more.

· - helps you detect potentially malicious websites. In addition, it provides more information about domains (IP addresses, DNS records, etc.) and cross-references them with known blacklists.

IoT Search Engine

The IoT (Internet of Things) search engine shows you devices connected to cyberspace - think Google search, but it's for connected devices. Why is this useful?

For example, instead of using Nmap to actively scan for ports and services, you can request existing available information about open ports, applications and protocols. is a popular Internet scanner with a public API and integration with many security tools. For marketers, it provides data about product users and their locations. Security researchers use it to discover vulnerable systems and access various IoT devices.