The external attack surface corresponds to the various potential entry points that malicious actors could use to gain access to an information system. Controlling the external attack surface by identifying and correcting vulnerabilities is therefore a crucial element of any IT security strategy.
Why is it so important to identify vulnerabilities on your external attack surface? What are the most common vulnerabilities? How can they be identified and corrected?
What is the external attack surface and why identify its vulnerabilities?
External attack surface: definition
The term "external attack surface" refers to the various points of entry to an information system, corresponding to assets exposed on the Internet. The external attack surface is made up of various "web services" in the broadest sense: websites, web applications, programming interfaces / APIs, remote access points, web servers, infrastructure components such as VPNs, firewalls and so on.
The size of the external attack surface is currently tending to grow, increasing at the same time the number of potential entry points. The various components of the external attack surface may indeed present vulnerabilities, security flaws and misconfigurations.
Reduce the risks associated with external threats
Because of their exposure on the Internet, the various components of the external attack surface are particularly vulnerable. Any uncorrected vulnerability can potentially become an attack vector, paving the way for further cyberattack. A malicious actor could, for example, successfully connect to a misconfigured web service, rebound on other equipment (pivot attack) and compromise the information system, culminating in successful data exfiltration. Controlling the attack surface is therefore an essential element of any effective threat prevention and detection strategy.
External attack surface: what are the most common vulnerabilities?
1. Unpatched software and hardware vulnerabilities
Unpatched software or operating system vulnerabilities are real security breaches, all the more so if the assets are exposed on the Internet.
A case in point are the "Zero-Day" vulnerabilities, detected by malicious actors before they have even been patched.
2. Identification and authentication failures (session management)
Misconfigured access controls can enable malicious actors to gain access to resources exposed on the Internet, or to successfully escalate privileges.
Example: poor management of privileged access (privileged accounts left as default).
3. Insecure APIs
APIs are normally used via an encrypted protocol. In the event of an API misconfiguration, a malicious actor can successfully compromise or exfiltrate data.
4. Open services and ports (firewall configuration problems)
Open ports are also important configuration faults, in the case of firewalls that have not been configured or have been configured incorrectly.
Examples: port 80 left open and unencrypted, port 21 left open, port 22 (SSH) for admin or root connections.
5. Failure to encrypt communications
Failure to encrypt communications encourages network sniffing and man-in-the-middle attacks. The use of weak encryption algorithms (or the absence of encryption) can enable malicious actors to recover identifiers in transit over the network. The risk is heightened when the network is exposed to the Internet.
6. Obsolete encryption
Similarly, older encryption algorithms can be exploited for malicious purposes.
- Encryption protocols to avoid: SSL V3, TLS 1.0, TLS 1.1
- Preferred encryption protocol: AES 956 minimum.
7. Internal network segmentation fault
Faulty network segmentation is considered a major vulnerability, as it facilitates compromise. Conversely, correctly segmenting your network according to needs reduces the risks, even more so if the architecture is properly filtered via a firewall.
For example: separate and isolate network zones as required, with some accessible via the Internet and others not, and add filtering and blocking measures in the event of suspected abnormal behavior.
8. Lack of control over components from external libraries
The use of components from external libraries has become virtually indispensable when creating new solutions. This can lead to a loss of control over external components. In this context, maintaining a high level of IT security requires regular vulnerability scans, as well as an awareness of the vulnerabilities published on the modules used. IT teams are then responsible for implementing the necessary corrections as part of their remediation plan.
Example: vulnerabilities in SSH modules.
9. Human vulnerabilities and social engineering attacks
Although not considered as vulnerabilities from a technical point of view, human vulnerabilities are nonetheless entry points that can be used to compromise an information system.
Example: distribution of login details for a business software application following a phishing email.
10. Monitoring failure
Monitoring generally concerns the management of a company's internal servers or services. It enables performance to be monitored by means of an alert system. A lack of monitoring does not constitute a vulnerability in the technical sense of the term, but it does present a risk in terms of IT security, since one of the aims of monitoring is to detect attacks in real time.
Example: the detection of a large number of connections to a service may indicate an attempt at a Distributed Denial of Service (DDoS) attack.
How to identify and correct vulnerabilities through a prevention strategy?
Proactive monitoring
To control your external attack surface and identify vulnerabilities, you need to know your system inside out. Mapping your information system, by listing the different operating systems and tools in use, makes it easier to monitor the various assets and detect any security flaws, configuration faults, etc., that may be present.
The use of vulnerability scans is also part of a proactive approach to IT security, which involves identifying threats and reducing them, rather than having to endure them.
Implement a vulnerability management policy
Detecting vulnerabilities on your attack surface is the first step. The next step is to put in place a vulnerability management policy consisting of :
- Assess vulnerabilities (in terms of severity, exploitability)
- Prioritize the treatment of vulnerabilities, taking into account the criticality of the assets concerned (critical and exploitable vulnerabilities linked to assets exposed on the Internet being the most urgent to correct).
- Draw up a remediation plan that defines an organization and processes dedicated to patch management, allocates the resources needed to implement security patches, monitors the frequency of security updates, etc.
Things to remember
With the number of assets exposed to the Internet soaring, vulnerability management of the external attack surface is of great importance when it comes to IT security. Knowing your external attack surface, being aware of the vulnerabilities most likely to affect it, and implementing a vulnerability management strategy are now essential practices for reducing external threats.
Find out how OverSOC can help you detect vulnerabilities in your external attack surface: contact us.
