Analysis

Continued from [Malware] Lazarus group’s Brambul worm of the former Wannacry - 1

Second routine

As soon as the second routine starts, three subroutines are called: sub_401ba0, sub_401b30, and sub_401040.

sub_401ba0

Create the lsasvc.exe file and run the process. Afterwards, access the shared folder as admin like the first routine.

sub_401b30

By adding a value named “WindowsUpdate” to the registry “Software \ Microsoft \ Windows \ CurrentVersion \ Run” path, the process will automatically run each time the computer is turned on.

sub_401040

Similar to what it did at the beginning of the program run, the gethostname function gets the user’s name.

After the three subroutines are executed, the GetVersion function is used to get the version of the operating system. I could see that it was classified as “WinNt”, “Win2000”, “WinVista”, “Win2003”, “WinXp”, and “Unkonwn”.

After that, it push the string whiat1001@gmail.com onto the stack and call the sub_401430 subroutine to send the data using the SMTP protocol. The sending account and mail server are the same as whiat1001 and gmail.com, but after pretending the sender account to johnS203@yahoo.com, the process ends. In sub_401430 we could see the strings related to SMTP and mail headers.

Behavior result