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Vol. 1 · Ed. 2026
CyberGlossary
Entry № 1036

Rhysida Ransomware

¿Qué es Rhysida Ransomware?

Rhysida RansomwareA ransomware-as-a-service group first observed in May 2023, known for targeting healthcare, education, and government victims and for high-profile attacks including the British Library and Insomniac Games breaches.


Rhysida is a ransomware-as-a-service group that emerged in May 2023 and quickly became one of the more active newcomers in the 2023–2025 cybercrime landscape, joining a wave of post-LockBit/post-ALPHV operators. The encryptor is written in C++ and uses AES-256 plus ChaCha20 hybrid encryption with file extensions changed to `.rhysida`, leaving the ransom note `CriticalBreachDetected.pdf`. Rhysida favors double-extortion: it exfiltrates data to its 'Rhysida' Tor leak site before encryption and lists victims publicly to pressure payment. The actor has hit a notably broad mix of sectors — local government, K-12 schools, hospitals (Prospect Medical, several U.K. NHS supply chains), the British Library (October 2023, a months-long outage), and Insomniac Games (Sony, December 2023). Initial access has included VPN credentials harvested by info-stealers, phishing, and exploitation of known vulnerabilities; affiliates often use Cobalt Strike, AnyDesk/Atera, and Mimikatz post-exploitation. CISA, the FBI, MS-ISAC, and U.K. NCSC published joint advisories on Rhysida TTPs in late 2023.

Ejemplos

  1. 01

    Rhysida claimed responsibility for the October 2023 British Library attack, which disrupted catalog, payment, and IT systems for many months.

  2. 02

    An MSSP detects Rhysida pre-encryption by alerting on Atera / AnyDesk installations on unmanaged servers, a recurring tradecraft pattern.

Preguntas frecuentes

¿Qué es Rhysida Ransomware?

A ransomware-as-a-service group first observed in May 2023, known for targeting healthcare, education, and government victims and for high-profile attacks including the British Library and Insomniac Games breaches. Pertenece a la categoría de Malware en ciberseguridad.

¿Qué significa Rhysida Ransomware?

A ransomware-as-a-service group first observed in May 2023, known for targeting healthcare, education, and government victims and for high-profile attacks including the British Library and Insomniac Games breaches.

¿Cómo funciona Rhysida Ransomware?

Rhysida is a ransomware-as-a-service group that emerged in May 2023 and quickly became one of the more active newcomers in the 2023–2025 cybercrime landscape, joining a wave of post-LockBit/post-ALPHV operators. The encryptor is written in C++ and uses AES-256 plus ChaCha20 hybrid encryption with file extensions changed to `.rhysida`, leaving the ransom note `CriticalBreachDetected.pdf`. Rhysida favors double-extortion: it exfiltrates data to its 'Rhysida' Tor leak site before encryption and lists victims publicly to pressure payment. The actor has hit a notably broad mix of sectors — local government, K-12 schools, hospitals (Prospect Medical, several U.K. NHS supply chains), the British Library (October 2023, a months-long outage), and Insomniac Games (Sony, December 2023). Initial access has included VPN credentials harvested by info-stealers, phishing, and exploitation of known vulnerabilities; affiliates often use Cobalt Strike, AnyDesk/Atera, and Mimikatz post-exploitation. CISA, the FBI, MS-ISAC, and U.K. NCSC published joint advisories on Rhysida TTPs in late 2023.

¿Cómo defenderse de Rhysida Ransomware?

Las defensas contra Rhysida Ransomware combinan habitualmente controles técnicos y prácticas operativas, como se detalla en la definición.

¿Cuáles son otros nombres para Rhysida Ransomware?

Nombres alternativos comunes: Rhysida.

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