The threat described pertains to a variant of the Locky ransomware identified around September 21-22, 2017. Locky ransomware is a type of malicious software that encrypts victims' files and demands payment for the decryption key. This particular variant is referenced with the suffix ".ykcol" and involves files named in the pattern "PIC_1234" and compressed archives such as "PIC_1234.7z". The mention of "Affid=3, offline" suggests this variant may operate in an offline mode, meaning it does not require active communication with a command and control server to encrypt files and execute its payload. Locky ransomware typically propagates via phishing emails containing malicious attachments or links, and once executed, it encrypts a wide range of file types, rendering them inaccessible to the user. The encrypted files are appended with a unique extension, in this case ".ykcol", signaling the infection. Victims are then presented with ransom notes demanding payment, often in cryptocurrency, to regain access to their data. The technical details indicate a threat level of 3 (on an unspecified scale) and a low severity rating, which may reflect the offline nature limiting its spread or impact compared to other variants. No known exploits in the wild or patches are associated with this variant, and no specific affected software versions are listed, as ransomware typically targets user data rather than software vulnerabilities. The lack of indicators and CWE entries suggests limited technical detail is available for this variant. Overall, this Locky variant represents a typical ransomware threat from 2017, with offline encryption capabilities and identifiable file markers.

For European organizations, the impact of this Locky ransomware variant can be significant despite its low severity rating. Ransomware infections can lead to loss of access to critical business data, operational disruption, and potential financial losses due to ransom payments or recovery costs. Offline operation means the ransomware can function without network connectivity, potentially increasing its effectiveness in isolated or segmented environments. European organizations with inadequate email filtering, user awareness, or endpoint protection are at risk of infection through phishing campaigns. The encryption of files with the ".ykcol" extension would disrupt normal business processes, especially if backups are not current or properly isolated. Additionally, the reputational damage and potential regulatory consequences under GDPR for data unavailability or loss could exacerbate the impact. However, the low severity and absence of known exploits suggest this variant may be less aggressive or widespread compared to other ransomware strains, possibly limiting its overall impact if proper defenses are in place.

To mitigate this Locky ransomware variant, European organizations should implement targeted measures beyond generic advice: 1) Enhance email security by deploying advanced phishing detection and sandboxing solutions to block malicious attachments and links before reaching end users. 2) Conduct regular, focused user awareness training emphasizing the identification and reporting of phishing attempts, particularly those involving suspicious compressed files like .7z archives. 3) Maintain robust, immutable, and offline backups of critical data to enable recovery without paying ransom, ensuring backups are regularly tested for integrity and restoration capability. 4) Employ endpoint detection and response (EDR) tools capable of identifying ransomware behavior patterns, including file encryption activities and unusual file extension changes such as ".ykcol". 5) Implement application whitelisting and restrict execution of unauthorized scripts or binaries that could trigger ransomware payloads. 6) Segment networks to limit lateral movement and isolate infected systems quickly. 7) Monitor file system changes and alert on mass encryption events or creation of suspicious archive files. These practical steps, tailored to the characteristics of this Locky variant, will reduce infection likelihood and improve incident response effectiveness.