The threat described pertains to a variant of the Locky ransomware, identified in mid-2017, which is distributed via malicious email attachments masquerading as legitimate invoice documents. The specific example given involves an email with a subject line "Copy of Invoice 87654321" and an attached ZIP file named "87654321.zip". Locky ransomware is known for encrypting victims' files and demanding ransom payments to restore access. This malware typically spreads through phishing campaigns where users are tricked into opening malicious attachments or enabling macros in Office documents. Once executed, Locky encrypts a wide range of file types on the infected system and connected network shares, rendering data inaccessible. The ransomware then displays ransom notes instructing victims on how to pay to recover their files. Although this particular instance is marked with a low severity and no known exploits in the wild at the time of reporting, Locky historically has been a significant threat due to its widespread distribution and impact on organizations. The technical details indicate a moderate threat level (3) and minimal analysis depth (1), suggesting limited additional technical data was available. The absence of affected versions or patches implies this is a malware campaign rather than a vulnerability in a specific product. Overall, this threat represents a classic ransomware infection vector leveraging social engineering and malicious attachments to compromise systems.

For European organizations, the impact of Locky ransomware can be substantial despite the low severity rating in this specific report. Successful infections can lead to loss of access to critical business data, operational disruption, financial losses due to ransom payments or recovery costs, and potential reputational damage. Sectors with high reliance on digital documents and invoicing, such as finance, healthcare, manufacturing, and public administration, are particularly vulnerable. The encryption of files can halt business processes and cause compliance issues, especially under GDPR regulations where data availability and integrity are critical. Additionally, lateral movement within networks can lead to widespread infection beyond the initially compromised endpoint. While this campaign was noted in 2017 and may not represent the latest Locky variants, the modus operandi remains relevant as similar phishing and ransomware tactics persist. European organizations must remain vigilant against such threats to avoid operational and financial impacts.

To mitigate the risk posed by Locky ransomware campaigns, European organizations should implement a multi-layered defense strategy. This includes: 1) Enhancing email security by deploying advanced spam filters and attachment sandboxing to detect and block malicious emails and ZIP attachments. 2) Conducting regular user awareness training focused on identifying phishing attempts and the dangers of opening unsolicited attachments or enabling macros. 3) Enforcing strict macro policies in Office applications, disabling macros by default, and only allowing digitally signed macros from trusted sources. 4) Maintaining up-to-date endpoint protection solutions capable of detecting ransomware behaviors and blocking execution. 5) Implementing robust backup procedures with offline or immutable backups to ensure rapid recovery without paying ransom. 6) Segmenting networks to limit lateral movement in case of infection. 7) Monitoring network traffic and endpoint activity for indicators of compromise related to ransomware. 8) Applying the principle of least privilege to reduce the impact of compromised accounts. These measures, combined with incident response planning and regular security assessments, will reduce the likelihood and impact of Locky ransomware infections.