Lucian Constantin
CSO Senior Writer

New JavaScript spam wave distributes Locky ransomware

news
May 27, 20162 mins

European countries are the most affected, but detections have also been recorded in the United States and Canada

Over the past week, computers throughout Europe and other places have been hit by a massive email spam campaign carrying malicious JavaScript attachments that install the Locky ransomware program.

Antivirus firm ESET has observed a spike in detections of JS/Danger.ScriptAttachment, a malware downloader written in JavaScript that started on May 22 and peaked on May 25.

Many countries in Europe have been affected, with the highest detection rates being observed in Luxembourg (67 percent), the Czech Republic (60 percent), Austria (57 percent), the Netherlands (54 percent), and the United Kingdom (51 percent). The company’s telemetry data also showed significant detection rates for this threat in Canada and the United States.

JS/Danger.ScriptAttachment can download various malware programs, but recently it has been used to primarily distribute Locky, a widespread, malicious program that uses strong encryption to hold users’ files hostage.

While Locky doesn’t have any known flaws that would allow users to decrypt their files for free, security researchers from Bitdefender have developed a free tool that can prevent Locky infections in the first place. The tool makes the computer appear as if it’s already infected by Locky by adding certain harmless flags, which tricks the malware into skipping it.

The use of JavaScript-based attachments to distribute Locky began earlier this year, prompting Microsoft to post an alert about it in April.

The attachments are usually .zip archive files that contain .js or .jse files inside. These files with will execute directly on Windows without the need of additional applications.

However, it is very uncommon for people to send legitimate applications written in JavaScript via email, so users should avoid opening this kind of file.

Lucian Constantin

Lucian Constantin writes about information security, privacy, and data protection for CSO. Before joining CSO in 2019, Lucian was a freelance writer for VICE Motherboard, Security Boulevard, Forbes, and The New Stack. Earlier in his career, he was an information security correspondent for the IDG News Service and Information security news editor for Softpedia.

Before he became a journalist, Lucian worked as a system and network administrator. He enjoys attending security conferences and delving into interesting research papers. He lives and works in Romania.

You can reach him at lucian_constantin@foundryco.com or @lconstantin on X. For encrypted email, his PGP key's fingerprint is: 7A66 4901 5CDA 844E 8C6D 04D5 2BB4 6332 FC52 6D42

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