Malware Analysis · May 14, 2019 · 3 min read

Parent PID Spoofing (Stage 2) Ataware Ransomware – Part 0x3

Ataware Ransomware Stage 2 uses Parent PID Spoofing technique to change its parent PID to lsass.exe and this article is also referred to in Mitre Attack website ^[4]. You may download the ATAPIConfiguration.exe file from ANY.RUN (MD5: 04a2e6400b22a3a5e5e277eceaf2ce0c)

Please check previous posts, if you are interested in the complete infection chain Excel 4.0 Macro Analysis – Ataware Ransomware Part 1 & UAC bypass analysis (Stage 1) Ataware Ransomware Part 2.

Overview of ATAPIConfiguration.exe (Stage 2)

Stage 2 downloads the final Ataware Ransomware (ATAPIUpdtr.exe) from CC which can encrypt files. Then, it uses Parent PID Spoofing to change the parent PID to lsass.exe before executing it.

Static Analysis
Parent PID Spoofing
Analysis steps in Ghidra
Conclusion
References

Static Analysis

32bit PE, compiled using GCC MINGW
Nothing interesting in overlay, no resources
Compiler timestamp invalid is 1997
File contain TLS callback but nothing interesting

Strings

Based on the strings berylia[.]net and /index/, we can guess that malware may be downloading something.
wininet.dll InternetConnectW berylia.net HttpOpenRequestW /index/ GET InternetQueryOptionW InternetSetOptionW HttpSendRequestA TEMP kernel32.dll CreateFileW InternetReadFile WriteFile InternetCloseHandle Advapi32.dll LookupPrivilegeValueW AdjustTokenPrivileges OpenThreadToken ImpersonateSelf SeDebugPrivilege CreateToolhelp32Snapshot Process32FirstW Process32NextW lsass.exe OpenProcess InitializeProcThreadAttributeList UpdateProcThreadAttribute CreateProcessA

Parent PID Spoofing

Stage 2 mainly uses InitializeProcThreadAttributeList, UpdateProcThreadAttribute & CreateProcessA with STARTUPINFOEXA structure API for spoofing. Didier Stevens already blogged about this in 2009 ^[1], “Normally the parent process of a new process is the process that created the new process (via CreateProcess). But when using STARTUPINFOEX with the right LPPROC_THREAD_ATTRIBUTE_LIST to create a process, you can arbitrarily specify the parent process, provided you have the debug rights.” Before spoofing, this Stage 2 enables SeDebugPrivilege of current thread.

UpdateProcThreadAttribute function^[2] is called with PROC_THREAD_ATTRIBUTE_PARENT_PROCESS (0x00020000) attribute with the handle of lsass.exe. At last, CreateProcessA is called with STARTUPINFOEXA Structure which contain new StartupInfoEx.lpAttributeList and creation flag 0x80010 (EXTENDED_STARTUPINFO_PRESENT | CREATE_NEW_CONSOLE) for creating new process with different Parent PID.

Parent PID Spoofing final code in Ghidra — Parent PID Spoofing final code

Analysis steps in Ghidra

1. Navigate to entry function, then to WinMain address @ 0x4013dd as shown below

Before any comment Main function Ghidra — Before any comment Main function

2. We will concentrate on download_spoof_parent_process_exe (0x40208b) in main function as shown below

3. Before any rename/comment @ 0x401cb7

Before Parent PID Spoofing function in Ghidra — Before Parent PID Spoofing function

4. This function contains two main functions FUN_00401b91() & FUN_00401579().
5. Let’s focus on FUN_00401b91 (adjust_priv_current_thread_sedebug), this function enables SeDebugPrivilege of current thread.

Adjust privilege of current thread Ghidra — Adjust privilege of current thread

Enable SeDebugPrivilege using AdjustTokenPrivileges

6. FUN_00401579()/download_save_ATAPIUpdtr_exe function download the file from CC hxxps://berylia[.]net/index/ and save it to $temp directory as ATAPIUpdtr.exe.

Download and save ATAPIUpdtr.exe - Using https, send GET request to CC

7. Parent PID Spoofing is shown below in the final code download_spoof_parent_process_exe.

Dynamic Analysis using Sysmon

File Create event Sysmon

Here you can see Process Create with spoofing in action with Parent Image lsass.exe.

Conclusion

Analysed Parent PID Spoofing and saw this in action using Sysmon
Malware uses this technique to evade detection which is based on parent-child process
We understood how malware author can enable SeDebugPrivilege

References

#ataware #ghidra #pe #ransomware #strings #sysmon