A new ransomware family discovered when analyzing a mid-scale campaign that started over the weekend uses decoy documents auto-synced to enterprise cloud storage and collaborations apps, security researchers have say.
Dubbed Spider, the new threat was observed being distributed via an Office document supposedly targeting users in Bosnia and Herzegovina, Serbia, and Croatia. The spam emails suggest the sender is looking to collect some debt from the recipient in attempt to trick the user into opening the attached file.
Obfuscated macro code embedded in the Office document, however, launches a Base64 encrypted PowerShell script to download the malicious payload, Netskope’s Amit Malik says.
If the malware is able to successfully infect a system, it starts encrypting user’s files and adds the ‘.spider’ extension the affected files.
A decrypter was designed to display the user interface and allow users decrypt the files using a decryption key. It is executed alongside the encrypter but runs in the background until the encryption process has been completed, BleepingComputer’s Lawrence Abrams explains.
According to Malik, the Spider decrypter monitors system processes and prevents the launch of tools such as taskmgr, procexp, msconfig, regedit, cmd, outlook, winword, excel, and msaccess.
During encryption, the malware skips files in the following folders: tmp, Videos, winnt, Application Data, Spider, PrefLogs, Program Files (x86), Program Files, ProgramData, Temp, Recycle, System Volume Information, Boot, and Windows.
After completing the encryption process, the decrypter displays a warning (available in English and Croatian) informing users on how they can decrypt their files. A help section is also included, with links and references to the resources needed to make the payment.
The ransom payment demanded is roughly $120.
“As ransomware continues to evolve, administrators should educate employees about the impact of ransomware and ensure the protection of the organization’s data by making a regular backup of critical data. In addition to disabling macros by default, users must also be cautious of documents that only contain a message to enable macros to view the contents and also not to execute unsigned macros and macros from untrusted sources,” Netskope says.
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