The threat described pertains to the Locky ransomware variant active around October 2017. Locky is a well-known ransomware family that encrypts victims' files and demands a ransom payment for decryption. This specific instance is identified by the presence of files with the extension ".ykcol" and filenames mimicking invoice documents, such as "Copy of invoice A1234567890..." and "InvoiceA1234567890.7z". The use of invoice-like filenames is a common social engineering tactic to entice users into opening malicious attachments or archives, which then execute the ransomware payload. Locky typically spreads via phishing emails containing malicious attachments or links. Once executed, it encrypts a wide range of file types on the infected system, appending unique extensions (here, ".ykcol") to encrypted files, rendering them inaccessible without the decryption key held by the attackers. The ransomware's offline status and low severity rating in this report suggest that this particular variant or campaign is no longer active or widespread, and no known exploits are currently in the wild for this specific sample. However, Locky historically caused significant disruption to organizations by encrypting critical data and demanding ransom payments, often in Bitcoin, to restore access. The technical details indicate a moderate threat level (3 out of an unspecified scale) and minimal analysis depth (1), implying limited available information on this specific sample. The absence of affected versions and patch links further suggests this is a malware campaign rather than a vulnerability in software products.

For European organizations, the impact of Locky ransomware can be substantial, particularly for entities that rely heavily on digital documents and invoicing systems. Successful infection leads to encryption of critical business files, causing operational downtime, loss of data integrity, and potential financial losses due to ransom payments or recovery costs. The use of invoice-themed lures increases the likelihood of infection in finance, accounting, and procurement departments, which are common targets in European enterprises. Additionally, encrypted data loss can lead to regulatory compliance issues under GDPR, especially if backups are insufficient or data recovery is delayed. While this specific variant is noted as offline and low severity, the historical impact of Locky ransomware campaigns underscores the importance of vigilance. European organizations with inadequate email filtering, user training, or endpoint protection remain at risk from similar ransomware threats that employ social engineering tactics.

To mitigate risks from Locky ransomware and similar threats, European organizations should implement targeted measures beyond generic advice: 1) Enhance email security by deploying advanced filtering solutions that detect and quarantine suspicious attachments, especially those with archive formats (.7z, .zip) and invoice-related filenames. 2) Conduct focused user awareness training emphasizing the risks of opening unsolicited invoice attachments and recognizing phishing attempts. 3) Implement application whitelisting to prevent execution of unauthorized scripts or executables from email attachments or temporary folders. 4) Maintain robust, immutable, and regularly tested backups stored offline or in segregated networks to enable rapid recovery without paying ransom. 5) Employ endpoint detection and response (EDR) tools capable of identifying ransomware behavior patterns early, such as rapid file encryption or creation of ransom notes. 6) Monitor network traffic for unusual activity indicative of ransomware propagation or command-and-control communication. 7) Apply strict access controls and segmentation to limit ransomware spread within corporate networks. These measures, combined with incident response planning specific to ransomware scenarios, will reduce the likelihood and impact of infections.