Google Drive and Microsoft Office 365, both of which have built-in malware protection, failed to identify a new form of Gojdue ransomware dubbed Shurl0ckr. The zero-day ransomware evaded most major antivirus platforms: only seven percent of 67 tested tools detected it.
Researchers on the Bitglass Threat Research Team discovered Shurl0ckr during a scan of malware in the cloud. It was confirmed as a form of ransomware-as-a-service by Cylance.
Shurl0ckr works the same way as Satan ransomware. A hacker creates a ransomware payload and distributes it via phishing or drive-by download. The malware encrypts files on disk in the background until the victim pays a Bitcoin ransom. Hackers pay a percentage to the author.
The discovery was part of a broader study on malware in the cloud. Researchers found 44% of businesses they scanned had some form of malware in at least one of their cloud applications. One in three corporate instances of SaaS applications were infected with malware.
Microsoft OneDrive had the highest rate of infection compared with other major SaaS applications, with 55% of instances hit. Google Drive was next-highest at 43%, followed by Box and Dropbox, both of which had a 33% infection rate.
Researchers dug into which file types are most likely to have malware. Script and executable formats were most common at 42%, followed by Office documents (21%), other file formats like text files and images (19%), Windows system files (10%), and compressed formats (8%).
The average business has nearly 450,000 files in the cloud, they report, and 1 in 20,000 contains malware, they report in their findings.