EASM – External attack surface management: what are we talking about ?

Nancy

9 August 2024

Awareness and resources, Not classified

Over the past decade, organizations have considerably increased their exposure surface, notably through the digitization of services and the use of cloud providers. For example, they have multiplied the number of public IP addresses to facilitate exchanges between their internal network and the Internet. As a result, corporate assets are increasingly exposed externally, some of them unmapped, unmonitored or even unknown to IT or cyber departments. The external attack surface has thus expanded to include resources managed by external service providers. External Attack Surface Management, or EASM, takes these issues into account.

External Attack Surface Management (EASM) is an approach to IT security which aims to detect, evaluate and control potential external access to an organization’s network or IT system. The aim : to reduce the risk of attacks on this perimeter.

What is EASM (External Attack Surface Management) ?

The external attack surface, also known as the “digital attack surface“, represents all the potential vulnerabilities that an attacker can target from outside the company in an attempt to compromise security. These entry points can include, for example :

Attackers seek to identify and exploit these weak points to penetrate the corporate information system, steal sensitive data, disrupt operations or carry out other malicious actions. That’s why it’s essential for companies to map and understand their external attack surface, and take steps to protect their assets by closing security gaps and implementing appropriate protection mechanisms.

Mapping, penetration testing and security audits are often carried out to assess the external attack surface and identify vulnerabilities before an attacker can exploit them.

What's the difference between ASM and EASM ?

Like EASM, Attack Surface Management, or ASM, is a cybersecurity strategy designed to identify, assess and manage potential vulnerabilities or access points in an IT system, with the aim of reducing the risk of attack. In essence, ASM aims to identify the global attack surface. To do this, we need to see things from an attacker’s point of view, and use the same methods that an attacker might use. This means describing the attack vectors that could be exploited by cybercriminals, be they security flaws in web applications, firewalls, operating systems or even IoT devices. ASM also protects against social engineering attacks – notably phishing – as well as physical attacks – when an attacker enters the target company’s premises.

EASM, on the other hand, concerns only external vulnerabilities and risks, i.e. those exposed on the Internet. Once the attack surface has been determined, EASM can be mobilized to assess the risks inherent in each access point, and also to prioritize the security actions required to circumvent them. As you can see, ASM and EASM are two fairly similar, even sometimes confused, approaches to cybersecurity, differing mainly only in the scope of their actions.

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