The ASEC analysis team has been continuously monitoring Magniber, ransomware that is distributed via Internet Explorer (IE) vulnerabilities. For the last couple of years, the attacker behind Magniber has been exploiting IE vulnerabilities to deploy ransomware. And as shown in the previous blog below, it is still being distributed by exploiting the IE vulnerabilities. What’s new, however, is that Magniber’s distribution has been confirmed on browsers other than IE: Microsoft Edge and Google Chrome.
This blog post aims to explain the distribution process of Magniber in the two browsers above.
Figure 1 and Figure 2 show distribution pages opened with Edge and Chrome, respectively. Both pages prompt users to install Windows application package file (.appx) to update the corresponding browser.
Note that the APPX file disguised as Chrome or Edge’s Windows update application internally contains a valid certificate (see Figure 3). This means that the Windows application (.appx) is sorted as a trusted application, therefore allowing its installation.
Figure 4 shows the result of executing the downloaded APPX file which is the creation of malicious EXE and DLL in the child paths of C:\Program Files\WindowsApps.
Figure 5 shows the code of the created EXE file (wjoiyyxzllm.exe). It loads the DLL file (wjoiyyxzllm.dll) that was created together and executes a specific function (mbenooj).
Figure 6 is a part of the DLL code that downloads the ransomware’s encoded payload and decodes it.
Ultimately, Magniber is executed from the memory of wjoiyyxzllm.exe, encrypting the user’s files and creating a ransom note demanding the user to send money if they wish to restore the files (Figure 7).
Magniber’s distributor signed the APPX file with a trusted certificate to disguise it as an innocuous app to deceive the system. Users must refrain from accessing untrusted websites and maintain security software such as V3 to the latest version.
exe loader: Trojan/Win.Loader.R462129 (2022.01.03.02)
Magniber dll: Ransomware/Win.Magniber.R462664 (2022.01.06.00), Ransomware/Win.Magniber.X2130 (2022.01.06.02)