The Locky ransomware family that dominated the charts last year has returned, and has been distributed through high volume campaigns over the past week.
Closely tied to the activity of the Necurs botnet, Locky has been nearly completely absent from the threat landscape this year. Following several months of total silence, the ransomware was present in spam runs in April and May, but went under the radar within weeks, as Necurs switched to distributing the Jaff ransomware.
On August 9, however, new spam campaigns dropping Locky caught the attention of security researchers. The first to observe the new ransomware variant was Racco42, who revealed that the spam messages contained subject lines similar to E [date] (random_numer).docx.
The Locky variant featured in that campaign was appending the .diablo6 extension to encrypted files and was downloaded by a VBS script packed inside a ZIP attachment. The malware demands a 0.49 Bitcoin ransom (currently about $2,250).
According to Fortinet, the malicious emails were mainly targeted at victims in the United States (37%) and Austria (36%). A large portion of them (10%) hit users in the UK. The security researchers also note that the new Locky variant packs the same capabilities as the last year version, and that free decryption isn’t possible.
Comodo, which performed a detailed analysis of the recent Locky attacks, calls the new ransomware variant IKARUSdilapidated, based on the appearance of the word in the code string. The security firm also says that tens of thousands of phishing emails featuring subject lines and attachments named similar to E [date] (random_numer) were observed over the course of several days dropping Locky.
A closer look at these emails revealed that 11,625 different IP addresses from 133 countries were used in this campaign, with Vietnam, India, Mexico, Turkey, and Indonesia being the top five. Most of the IP owners are telecom companies and ISPs, meaning that they belong “to infected, now compromised computers,” essentially forming a botnet, Comodo notes in a report shared with SecurityWeek.
Earlier this week, another Locky variant emerged, one that would append the .Lukitus extension to the encrypted files, Malwarebytes says. The spam emails feature either no subject or something similar to Emailing – CSI-034183_MB_S_7727518b6bab2 as subject line, and include a RAR or ZIP attachment that has JS files inside, which in turn download Locky.
To stay protected, users should keep their files backed up at all times and should also avoid opening attachments or clicking on links coming via email from unknown sources. Keeping the operating system and all applications on the computer updated at all times should also prevent infections from happening.
“It’s still too early to say if this campaign signals the start of Locky diving back into the ransomware race or if it is just testing the waters. We’ll probably see in the next few weeks or months,” Fortinet says.
Related: Necurs Botnet Distributing Locky Ransomware via Fake Invoices