External Recon

What are we looking for?

Data Point Description
IP Space Valid ASN for our target, netblocks in use for the organization's public-facing infrastructure, cloud presence and the hosting providers, DNS record entries, etc.
Domain Information Based on IP data, DNS, and site registrations. Who administers the domain? Are there any subdomains tied to our target? Are there any publicly accessible domain services present? (Mailservers, DNS, Websites, VPN portals, etc.) Can we determine what kind of defenses are in place? (SIEM, AV, IPS/IDS in use, etc.)
Schema Format Can we discover the organization's email accounts, AD usernames, and even password policies? Anything that will give us information we can use to build a valid username list to test external-facing services for password spraying, credential stuffing, brute forcing, etc.
Data Disclosures For data disclosures we will be looking for publicly accessible files ( .pdf, .ppt, .docx, .xlsx, etc. ) for any information that helps shed light on the target. For example, any published files that contain intranet site listings, user metadata, shares, or other critical software or hardware in the environment (credentials pushed to a public GitHub repo, the internal AD username format in the metadata of a PDF, for example.)
Breach Data Any publicly released usernames, passwords, or other critical information that can help an attacker gain a foothold.

Where Are We Looking?

Resource Examples
ASN / IP registrars IANA, arin for searching the Americas, RIPE for searching in Europe, BGP Toolkit
Domain Registrars & DNS Domaintools, PTRArchive, ICANN, manual DNS record requests against the domain in question or against well known DNS servers, such as
Social Media Searching Linkedin, Twitter, Facebook, your region's major social media sites, news articles, and any relevant info you can find about the organization.
Public-Facing Company Websites Often, the public website for a corporation will have relevant info embedded. News articles, embedded documents, and the "About Us" and "Contact Us" pages can also be gold mines.
Cloud & Dev Storage Spaces GitHub, AWS S3 buckets & Azure Blog storage containers, Google searches using "Dorks"
Breach Data Sources HaveIBeenPwned to determine if any corporate email accounts appear in public breach data, Dehashed to search for corporate emails with cleartext passwords or hashes we can try to crack offline. We can then try these passwords against any exposed login portals (Citrix, RDS, OWA, 0365, VPN, VMware Horizon, custom applications, etc.) that may use AD authentication.

Finding Address Spaces

Address blocks assigned to an organization: BGP-Toolkit hosted by Hurricane Electric


Validate our scope and find out about reachable hosts the customer did not disclose in their scoping document. Sites like domaintools, and viewdns.info.

Public Data

Social media can clue us in to how the organization is structured, what kind of equipment they operate, potential software and security implementations, their schema, and more. Also, job-related sites like LinkedIn, Indeed.com, and Glassdoor.

Example Enumeration Process

Example on the LEGALCORP.com domain without performing any heavy scans.

Check BGP-Toolkit

  • IP Address:
  • Mail Server: mail1.LEGALCORP.com
  • Nameservers: NS1.LEGALCORP.com & NS2.LEGALCORP.com

Utilize viewdns.info to validate the IP address of our target. Both results match, which is a good sign. Let's try another route to validate the two nameservers in our results.

neutron@kali[/kali]$ nslookup ns1.LEGALCORP.com


Non-authoritative answer:
Name:   ns1.LEGALCORP.com

nslookup ns2.LEGALCORP.com

Non-authoritative answer:
Name:   ns2.LEGALCORP.com

We now have two new IP addresses to add to our list for validation and testing. Before taking any further action with them, ensure they are in-scope for your test.

LEGALCORP is a fictitious company, so there is no real social media presence. However, we would check sites like LinkedIn, Twitter, Instagram, and Facebook for helpful info if it were real.

Looking for any documents. Using filetype:pdf inurl:LEGALCORP.com as a search, we are looking for PDFs.

Using intext:"@LEGALCORP.com" inurl:LEGALCORP.com, we are looking for any instance that appears similar to the end of an email address on the website. One promising result came up with a contact page.

Browsing the contact page, we can see several emails for staff in different offices around the globe. We now have an idea of their email naming convention (first.last) and where some people work in the organization. This could be handy in later password spraying attacks or if social engineering/phishing were part of our engagement scope.