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Cyber Threat
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Ransomware victim Financial Services

Hannover Re

Listed by Silentransomgroup on · organisation based in Germany

hannover-re.com

Disclosed
May 6, 2025
Leak-site listing date
Threat group
Silentransomgroup
205 victims listed
Country
Germany
#2 most targeted
Sector
Financial Services

ThreatAI analysis

Compiled from this incident record and the threat intelligence profile for Silentransomgroup. Figures and technique mappings are quoted from the source data, not inferred.

About the Silentransomgroup group

A former Conti team aka Chatty Spider and UNC3753 Silentransomgroup has listed 160 victims since June 2022.

How Silentransomgroup is documented to operate

Valid Accounts T1078 Stealth Persistence

Adversaries may obtain and abuse credentials of existing accounts as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Compromised credentials may be used to bypass access controls placed on various resources on systems within the network and may even be used for persistent access to remote systems and externally available services, such as VPNs, Outlook Web Access, network devices, and remote desktop. Compromised credentials may also grant an adversary increased privilege to specific systems or access to restricted areas of the network.

Mitigations: Application Developer Guidance, User Training, Password Policies, User Account Management, Privileged Account Management, Multi-factor Authentication

MITRE ATT&CK reference
Phishing T1566 Initial Access

Adversaries may send phishing messages to gain access to victim systems. All forms of phishing are electronically delivered social engineering. Phishing can be targeted, known as spearphishing. In spearphishing, a specific individual, company, or industry will be targeted by the adversary. More generally, adversaries can conduct non-targeted phishing, such as in mass malware spam campaigns. Adversaries may send victims emails containing malicious attachments or links, typically to execute malicious code on victim systems. Phishing may also be conducted via third-party services, like social media platforms.

Mitigations: Network Intrusion Prevention, Restrict Web-Based Content, User Training, Antivirus/Antimalware, Software Configuration, Audit

MITRE ATT&CK reference
Data from Cloud Storage T1530 Collection

Adversaries may access data from cloud storage. Many IaaS providers offer solutions for online data object storage such as Amazon S3, Azure Storage, and Google Cloud Storage. Similarly, SaaS enterprise platforms such as Office 365 and Google Workspace provide cloud-based document storage to users through services such as OneDrive and Google Drive, while SaaS application providers such as Slack, Confluence, Salesforce, and Dropbox may provide cloud storage solutions as a peripheral or primary use case of their platform.

Mitigations: Filter Network Traffic, User Account Management, Restrict File and Directory Permissions, Multi-factor Authentication, Audit, Encrypt Sensitive Information

MITRE ATT&CK reference
Archive Collected Data T1560 Collection

An adversary may compress and/or encrypt data that is collected prior to exfiltration. Compressing the data can help to obfuscate the collected data and minimize the amount of data sent over the network. Encryption can be used to hide information that is being exfiltrated from detection or make exfiltration less conspicuous upon inspection by a defender. Both compression and encryption are done prior to exfiltration, and can be performed using a utility, 3rd party library, or custom method.

Mitigations: Audit

MITRE ATT&CK reference
Exfiltration over USB T1052.001 Exfiltration

Adversaries may attempt to exfiltrate data over a USB connected physical device. In certain circumstances, such as an air-gapped network compromise, exfiltration could occur via a USB device introduced by a user. The USB device could be used as the final exfiltration point or to hop between otherwise disconnected systems.

Mitigations: Limit Hardware Installation, Data Loss Prevention, Disable or Remove Feature or Program

MITRE ATT&CK reference
Exfiltration Over Web Service T1567 Exfiltration

Adversaries may use an existing, legitimate external Web service to exfiltrate data rather than their primary command and control channel. Popular Web services acting as an exfiltration mechanism may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to compromise. Firewall rules may also already exist to permit traffic to these services. Web service providers also commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Mitigations: Restrict Web-Based Content, Data Loss Prevention

MITRE ATT&CK reference

MITRE ATT&CK techniques attributed to Silentransomgroup across its recorded activity, not a finding about how Hannover Re was reached.

Incident analysis

Hannover Re was listed by Silentransomgroup ransomware, a group with 205 victims recorded in this database. The listing appeared on the group's leak site on May 6, 2025.

Hannover Re is based in Germany and operates in the Financial Services sector. Germany ranks #2 worldwide for ransomware disclosures, with 1,041 victims in this database.

Sector context. Financial sector organisations are targeted for their access to funds, sensitive financial data, and the reputational damage a public breach can cause. Regulatory requirements also increase recovery costs.

Silentransomgroup typically follows a double extortion model: data is exfiltrated from the victim's systems before files are encrypted, so the victim faces two demands at once — pay to restore access, and pay to keep stolen data unpublished. The leak site, where this listing appeared, is the lever for the second demand.

Source. Public leak-site disclosures aggregated via the ransomware.live API. The disclosure date is when the listing was published, which can differ from the date of compromise. This site does not publish or link to stolen data. Last updated .

Frequently asked questions

Was Hannover Re attacked by ransomware?

Yes. Hannover Re was listed as a victim of the Silentransomgroup ransomware group on May 6, 2025. The organisation is based in Germany and operates in the Financial Services sector. The disclosure appeared on the group's dark web leak site.

Which ransomware group attacked Hannover Re?

Hannover Re was attacked by Silentransomgroup ransomware. Silentransomgroup is one of the most active ransomware groups, having claimed 205 victims globally. The group typically employs a double-extortion model: encrypting the victim's files and threatening to publish stolen data.

When did the Hannover Re ransomware attack occur?

The ransomware attack on Hannover Re was disclosed on May 6, 2025. This date reflects when the victim was published on the threat group's leak site, which may differ from the actual date of initial compromise.

What data was stolen in the Hannover Re ransomware attack?

The specific data stolen from Hannover Re has not been independently verified by this platform. Ransomware groups typically exfiltrate data before encrypting systems and use the threat of publication to pressure victims. As a Financial Services organisation, Hannover Re likely held financial records, client data, and transaction histories.

How can organisations protect against Silentransomgroup attacks?

To defend against Silentransomgroup and similar threat actors, organisations should: maintain regular offline backups tested for restoration; implement network segmentation to limit lateral movement; deploy multi-factor authentication on all remote access; use endpoint detection and response (EDR) tools; conduct regular phishing and security awareness training; and monitor threat intelligence feeds for indicators of compromise (IOCs) associated with active groups.