Rapidly Changing Infection Method of BlueCrab Ransomware (feat. notepad.exe)

AhnLab ASEC Analysis Team has been monitoring BlueCrab(=Sodinokibi) ransomware in form of Javascript distributed via phishing download page. The phishing download page is masquerading as the one to download utilities, and appears on the top of Google search results as Figure 1. This is a well-known technique that has been frequently used by others including GandCrab ransomware. Although the Javascript distribution method remains as is, a new change in Javascript code has been detected. Moreover, the pace of change is…

Be Careful with Excel File Disguised as ‘Wage Statement’ Distributed via Email

Users should be careful as many spam emails with downloader malware targeting Korean companies have been distributed. The titles of detected spam emails are “October Wage Statement” and “Estimate for XX”. These spam mails attach Microsoft Office Excel document files by the name of “QF001_1093_101819.xls” and “P001_102019_4472.xls” or direct to phishing webpage disguised as OneDrive to prompt users to download malware. The sender is “Kim Sun-ah” but the title and content are likely to change.   When a malicious excel file is run, the screen appears to prompt users to use the macro. Once it is allowed, the malicious macro is executed. Upon allowing the use of macro, a loading screen pops up while the macro is run. The macro…

New Stealer’s Suspicious Relationship with State-Sponsored Ryuk Ransomware?

AhnLab’s security analysts recently discovered a new stealer targeting to steal personal information. Apart from the new stealer’s purpose and how it works, similarities with the Ryuk ransomware was also an attention grabber. Ryuk ransomware, first found in 2018, is known to target specific countries.  The new stealer searches for files on infected systems that match specific conditions, such as extension, size, and names. Then it verifies if certain keywords are present in the files and transmits them to the…

[Warning] Emotet Malware Distributed in the form of Document File

AhnLab ASEC analysis team has confirmed that Word files containing malicious VBA macro are distributed to Korean users. The malicious VBA macro uses WMI to run powershell and download Emotet malware. As the Word file is executed, users will see a figure below that prompts them to run VBA macro. Prompting messages are being distributed in various forms, as seen in Figure 2. A distributed VBA macro is obfuscated by using junk codes and annotations, as seen in Figure 3. Figure 4 is a deobfuscated VBA macro.    Our code analysis revealed that the currently distributed macro uses WMI(winmgmts:Win32_Process) to run powershell, whereas the VBA macro discovered in November of 2018 utilized cmd. The powershell command executed via WMI is encoded with Base64, as seen…

Trick or Treat! Corporate targeting Trickbot

Trickbot, orginally a banking Trojan, aims to collect and leak corporate confidential information. Recently, attackers have distributed fake Word files and obfuscated scripts to trick corporate users in downloading the Trickbot downloader. Thereby, extra attention is required to prevent downloading Tickbot. When the user opens the Word document attachment in the email, it will tell the user to click the “Enable Content” button with the message, “Document created in the previous version,” as shown in Figure 1. However, this is…