The provided information references a guide on relaying NTLM authentication over HTTP, using the example of GLPI, an open-source IT asset management and service desk software. NTLM (NT LAN Manager) is a Microsoft authentication protocol that, if improperly handled, can be vulnerable to relay attacks. In such attacks, an adversary intercepts NTLM authentication requests and forwards them to another service, effectively impersonating the legitimate user without needing their password. The guide appears to demonstrate how NTLM authentication can be relayed over HTTP, potentially allowing attackers to gain unauthorized access to GLPI instances or other services relying on NTLM authentication. Although no specific vulnerabilities or affected versions are listed, the medium severity rating suggests that the technique could be leveraged in internal penetration testing scenarios or targeted attacks where NTLM authentication is in use. The lack of known exploits in the wild indicates this is more of a proof-of-concept or educational material rather than an active widespread threat. However, organizations using GLPI or other NTLM-reliant services should be aware of the risks posed by NTLM relay attacks, especially if their network segmentation or authentication protections are weak. The guide likely details the technical steps to perform such relays, emphasizing the need for proper mitigation strategies such as enforcing SMB signing, using Kerberos instead of NTLM where possible, and restricting relay attack vectors through network controls.

For European organizations, the potential impact of NTLM relay attacks is significant in environments where legacy authentication protocols like NTLM are still in use, particularly in internal networks. Successful relay attacks can lead to unauthorized access to critical IT service management platforms like GLPI, which may contain sensitive asset, user, and incident data. This could result in data breaches, unauthorized changes to IT infrastructure, and disruption of service desk operations. Additionally, compromised credentials through relay attacks can be leveraged for lateral movement within corporate networks, increasing the risk of broader compromise. Given the medium severity and the internal nature of such attacks, the impact is primarily on confidentiality and integrity, with availability potentially affected if attackers disrupt service management processes. European organizations with complex IT environments, legacy systems, or insufficient network segmentation are at higher risk. Furthermore, compliance with GDPR and other data protection regulations means that any unauthorized access or data leakage could lead to regulatory penalties and reputational damage.

To mitigate the risk of NTLM relay attacks in European organizations, the following specific measures should be implemented: 1) Disable NTLM authentication where possible and migrate to Kerberos, which is more secure against relay attacks. 2) Enforce SMB signing and channel binding on all systems to prevent interception and relay of NTLM credentials. 3) Implement strict network segmentation and firewall rules to limit the ability of attackers to relay authentication requests across different network segments. 4) Use Extended Protection for Authentication (EPA) features on Windows servers and services to bind authentication to specific channels. 5) Regularly audit and monitor authentication logs for unusual NTLM authentication patterns or relay attempts. 6) Harden GLPI and similar platforms by applying the latest security updates and configuring authentication settings to minimize exposure to relay attacks. 7) Educate internal security teams about NTLM relay attack techniques and detection methods, leveraging the guide as a training resource. 8) Consider deploying intrusion detection systems capable of identifying NTLM relay attack signatures within internal network traffic.