Internet-facing assets like domains, servers, or networked device endpoints are where attackers look first, probing their target’s infrastructure to determine if there is a viable way in. External attack surface management (EASM) is how security teams stay ahead of such vulnerabilities, which is why it’s become so critical for shoring up defences.
However, many security teams only rely on Microsoft Defender for EASM, which might not be enough. We regularly see some of the most security-mature organisations suffer breaches, indicating that there are some gaps in how EASM is being implemented across industries.
How EASM Blind Spots Become Entry Points
With powerful, widely available scanners like Shodan, Censys, or custom-built scanners, attackers are always probing the internet to identify any exposed assets. Something as simple as an open port or misconfigured server can signal to them that a service is active and potentially exploitable.
In more targeted attacks, a malicious actor might even correlate data from multiple sources to map the target’s entire external footprint. This may include exposed admin panels coupled with leaked secrets on GitHub, or open APIs with weak or missing authentication.
Because our digital footprints are so extensive nowadays, there is a real challenge in maintaining visibility and control across all assets. Even the most powerful companies are struggling. In the spring of 2025, Oracle, a leading provider of cloud infrastructure services, suffered a breach that exposed millions of customer records.
The cause was a single unmanaged subdomain, which attackers used to gain initial access and identify other security gaps before moving laterally.
The Most Common EASM Blind Spots
Regardless of how much emphasis is placed on EASM, exposures still can and do happen. There are simply too many dynamics at work. Perhaps the most obvious one is the rise of remote work policies, which significantly accelerated the spread of shadow IT.
Employees now often use their own devices for work, which includes any applications or services installed that the company’s IT team has no idea about. Without integration into the EASM inventory, such assets are a major blind spot for defenders and a huge opportunity for attackers.
Old infrastructure is another blind spot. Old servers, domains, or staging environments regularly outlive their purpose. Even though they’re not in use, they remain online and unpatched. Without security updates or proper configuration management, these are the easiest targets.
Because businesses are so interconnected, third-party risk is another gap. Organisations have very little control over how their partners secure and manage their infrastructure, outside of any initial due diligence, before starting the relationship.
With so many possible exposures, relying on a single tool to identify them adds to the risk. Most companies only use Defender, which is a great tool, but it also gives false confidence that all internet-facing assets are accounted for.
Does AI Close or Create More Blind Spots?
A big topic around EASM and cybersecurity in general is the impact of artificial intelligence and how it aids attackers and defenders.
On the offensive side, AI has made it slightly easier for attackers to automate reconnaissance by generating exploit scripts or analysing vast amounts of publicly available data. The main advantage adversaries get is speed, which is crucial when a missing a patch install by a day can turn into a security incident.
For defenders, the benefits are equally significant. Modern EASM platforms leverage AI to improve asset discovery, correlate data across the environment, and prioritise findings based on asset criticality and exploitability.
So it’s a double-edged sword, and it’s unlikely that AI will create any meaningful advantage for either side, as both parties are constantly adapting.
Hardening Your External Attack Surface Management
If you’re already implementing EASM, a few small tweaks can have a huge impact in reducing external exposure.
The frequency of scanning is very important. Adversaries don’t scan your infrastructure just once per quarter, and neither should you. Scanning should be continuous, with automated discovery across domains, endpoints, IPs, and cloud instances. Any old or unused infrastructure that is discovered should be removed.
To improve the breadth of scanning, consider implementing an additional EASM layer on top of Defender. It’s important to incorporate validation and remediation capabilities, particularly surrounding unmanaged SaaS applications, external cloud providers, and third-party relationships.
Once your EASM stack is in order, it’s best to integrate it with your SIEM, SOAR, DRPS and ticketing workflows. This way, security teams can easily analyse external exposure findings and implement any necessary fixes, prioritised by risk levels.
Final Thoughts
The effectiveness of your security program depends on what you can see, but even more so on what you can’t. EASM has become one of the most valuable tools for uncovering exposures before attackers do. But it’s not a silver bullet. Blind spots will always exist where visibility, context, or ownership breaks down.