Telefónica Breach Incident Score: Analysis & Impact (TEL1766404766)

In this Rankiteo incident briefing, we review the Telefónica breach identified under incident ID TEL1766404766.

The analysis begins with a detailed overview of Telefónica's information like the linkedin page: https://www.linkedin.com/company/telefonica, the number of followers: 1279598, the industry type: Telecommunications and the number of employees: 119880 employees

After the initial compromise, the video explains how Rankiteo's incident engine converts technical details into a normalized incident score. The incident score before the incident was 634 and after the incident was 563 with a difference of -71 which is could be a good indicator of the severity and impact of the incident.

In the next step of the video, we will analyze in more details the incident and the impact it had on Telefónica and their customers.

On 22 December 2025, Telefónica Móviles (Movistar) disclosed Data Breach issues under the banner "Telefónica Móviles (Movistar) GDPR Violation Fine".

Telefónica Móviles, operating under the brand name Movistar, was fined €300,000 for breaching the EU’s GDPR data protection rules.

The disruption is felt across the environment, and exposing Personal data processed unlawfully during mobile phone line changes, plus an estimated financial loss of €300,000.

Formal response steps have not been shared publicly yet.

The case underscores how Completed (decision issued).

Finally, we try to match the incident with the MITRE ATT&CK framework to see if there is any correlation between the incident and the MITRE ATT&CK framework.

The MITRE ATT&CK framework is a knowledge base of techniques and sub-techniques that are used to describe the tactics and procedures of cyber adversaries. It is a powerful tool for understanding the threat landscape and for developing effective defense strategies.

Rankiteo's analysis has identified several MITRE ATT&CK tactics and techniques associated with this incident, each with varying levels of confidence based on available evidence. Under the Initial Access tactic, the analysis identified Valid Accounts (T1078) with moderate to high confidence (70%), supported by evidence indicating unlawful processing of personal data during mobile phone line changes. Under the Collection tactic, the analysis identified Data from Information Repositories (T1213) with moderate to high confidence (80%), supported by evidence indicating personal data processed unlawfully during mobile phone line transfers. Under the Exfiltration tactic, the analysis identified Exfiltration Over Alternative Protocol (T1048) with moderate confidence (60%), supported by evidence indicating gDPR-protected data mishandled (implied unauthorized transfer). Under the Impact tactic, the analysis identified Data Destruction (T1485) with moderate confidence (50%), supported by evidence indicating unlawful processing of personal data (potential misuse or loss) and Data Encrypted for Impact (T1486) with lower confidence (30%), supported by evidence indicating no direct evidence, but GDPR violation implies data handling risks. These correlations help security teams understand the attack chain and develop appropriate defensive measures based on the observed tactics and techniques.