The threat described is a malspam campaign distributing the Locky ransomware, observed on May 24, 2016. Locky ransomware is delivered via malicious spam emails containing a ZIP archive attachment. This archive includes a JavaScript (.js) file that, when executed, downloads additional payload data that is partially XOR-encoded and reversed to evade detection. The JavaScript loader decodes and executes the ransomware payload on the victim's machine. Locky ransomware encrypts user files, rendering them inaccessible, and demands a ransom payment for decryption. The campaign uses social engineering to trick users into opening the malicious attachment, often disguised as an invoice or other business-related document. Although the severity is marked as low in the source, Locky ransomware historically has caused significant disruption due to its file encryption capabilities and widespread distribution via email. The threat does not require exploiting a software vulnerability but relies on user interaction to execute the malicious script. No specific affected software versions are listed, indicating the attack targets end users indiscriminately rather than exploiting a particular software flaw. The campaign’s technical complexity includes obfuscation techniques such as partial XOR encoding and reversal of payload data to bypass signature-based detection mechanisms. No known exploits in the wild beyond the malspam vector are reported. Overall, this threat represents a classic ransomware distribution method leveraging social engineering and script-based payload delivery.

For European organizations, the Locky ransomware malspam campaign poses a significant risk primarily through potential data loss and operational disruption. If users open the malicious JavaScript attachment, critical files can be encrypted, leading to downtime and costly recovery efforts. The impact extends to confidentiality, as encrypted data may be inaccessible, and integrity, as files are altered by encryption. Availability is also affected due to system and data inaccessibility. European organizations with large email user bases and limited email filtering or user awareness training are particularly vulnerable. The campaign’s reliance on user interaction means that sectors with high email volumes and less stringent security awareness, such as SMEs, healthcare, and public administration, may be disproportionately impacted. Additionally, the ransomware’s presence can lead to reputational damage and potential regulatory consequences under GDPR if personal data is affected or if incident response is inadequate. Although the campaign is dated (2016), similar malspam techniques remain prevalent, and organizations must remain vigilant against such threats.

To mitigate this threat effectively, European organizations should implement multi-layered defenses beyond generic advice: 1) Deploy advanced email filtering solutions capable of detecting obfuscated scripts and suspicious ZIP attachments, including sandboxing to analyze attachments before delivery. 2) Enforce strict attachment policies that block or quarantine emails containing JavaScript files or double extensions (e.g., .zip with .js inside). 3) Conduct regular, targeted user awareness training focusing on recognizing malspam and the dangers of opening unexpected attachments, emphasizing the risks of enabling scripts. 4) Implement application whitelisting to prevent unauthorized execution of scripts and unknown binaries. 5) Maintain robust, tested offline backups of critical data to enable recovery without paying ransom. 6) Monitor network traffic for unusual outbound connections indicative of ransomware payload downloads. 7) Keep endpoint security solutions updated with behavioral detection capabilities to identify ransomware activity post-execution. 8) Establish incident response procedures specifically for ransomware infections, including rapid isolation and forensic analysis. These measures, combined, reduce the likelihood of successful infection and limit damage if an infection occurs.