The provided information concerns the resurgence of the Locky ransomware, distributed via the Necurs botnet, as highlighted in an OSINT threat spotlight by CIRCL dated April 2017. Locky ransomware is a type of malware that encrypts victims' files and demands ransom payments for decryption keys. The Necurs botnet is a large-scale spam distribution network known for propagating various malware strains, including ransomware like Locky. This campaign marks the return of Locky through Necurs, indicating a renewed threat vector leveraging spam emails to deliver malicious payloads. Although specific affected versions or detailed technical indicators are not provided, the threat level is noted as moderate (threatLevel: 3) with a low overall severity rating. The absence of known exploits in the wild suggests that the infection vector relies primarily on social engineering and spam campaigns rather than exploiting software vulnerabilities. The malware's impact typically involves encryption of user data, leading to potential data loss and operational disruption if backups are unavailable. The technical details and timestamps confirm this is a known ransomware campaign from 2017, with no new zero-day vulnerabilities indicated.

For European organizations, the return of Locky via Necurs poses a risk primarily through phishing and spam email campaigns. The impact includes potential data encryption leading to loss of access to critical files, operational downtime, and financial costs associated with ransom payments or recovery efforts. Organizations with insufficient email filtering, lack of user awareness training, or inadequate backup strategies are particularly vulnerable. The disruption can affect confidentiality and availability of data, with indirect impacts on integrity if data restoration is incomplete or corrupted. Given the widespread use of Microsoft Windows systems across Europe and the common reliance on email communications, the threat could affect a broad range of sectors including healthcare, finance, manufacturing, and public administration. However, the low severity rating and absence of active exploits suggest the threat is manageable with proper defenses.

To mitigate this threat, European organizations should implement advanced email filtering solutions capable of detecting and blocking spam and malicious attachments associated with Necurs and Locky campaigns. User awareness training is critical to reduce the risk of phishing-induced infections; employees should be trained to recognize suspicious emails and avoid opening unknown attachments or links. Regular, tested backups of critical data must be maintained offline or in immutable storage to ensure recovery without paying ransom. Endpoint protection platforms with behavioral detection can help identify and block ransomware activity early. Network segmentation can limit the spread of ransomware within organizational environments. Additionally, organizations should monitor threat intelligence feeds for updated indicators of compromise related to Necurs and Locky to enhance detection capabilities. Incident response plans should be reviewed and tested to ensure readiness in case of infection.