1. BERLIN • NEW YORK • SAN FRANCISCO • SÃO PAULO • PARIS • LONDON • MOSCOW • ISTANBUL SEOUL •
SHANGHAI • BEIJING • TOKYO • MUMBAI • SINGAPORE

2. 2
About Me
‣ Security Analyst
‣ Former Software Engineer
‣ Part of Adjust’s Fraud Team
‣ RiverBird.co
‣ @cheese0x2

3. What is Malware?
“Malware is a binary that does
something someone wouldn’t
like...”

4. Demo

5. Why bother with
analysis?

6. “Sacred Cash Cow Tipping”

7. Analyzing a
Ransomware

8. openme.exe

9. Static Analysis

10. Unix: ./strings openme.exe

11. Unix: ./strings openme.exe

12. Windows: PEStudio

13. Windows: PEStudio

14. Dynamic Analysis

15. Unix: ./fakedns.py

16. Unix: ./inetsim

17. What we know
- An encrypted POST request to brb.3dtuts.by
- Not a single call to WinInet is weird
- No reference to brb.3dtuts.by
- No sign of cryptography functions
- Too much noise in `./strings` output
- The use of TLS

18. Typical HTTP Imports
Courtesy of MSDN
(Microsoft Developer
Network)

19. Typical Cryptography Imports
Courtesy of MSDN
(Microsoft Developer
Network)

20. Checking for
Packers

21. Theory

22. Theory
Theory #1: Binary will use VirtualProtect to dump
a packed binary?
Theory #2: CryptEncrypt will be used
somewhere?

23. VirtualProtect
Courtesy of MSDN
(Microsoft Developer
Network)

24. Attach a Debugger
Windows: x32dbg

25. Windows: x32dbg
Breakpoint hit!

26. Checking Memory Regions
Found a newly created
memory region with
“ERW” permissions

27. Theory #1 was correct
Theory #1: Binary will use VirtualProtect to
dump a packed binary? YES
Theory #2: CryptEncrypt will be used
somewhere?

28. Theory #2: CryptEncrypt
We know now the malware is
unpacking itself. Let it finish...

29. CryptEncrypt
Courtesy of MSDN
(Microsoft Developer
Network)

30. Windows: x32dbg
Breakpoint hit!

31. MZ == ?

32. MZ == Profit $$$

33. Theory #2 was correct
Theory #1: Binary will use VirtualProtect to
dump a packed binary? YES
Theory #2: CryptEncrypt will be used
somewhere? YES

34. Unix: ./strings dumped_bin
HTTP and
Cryptography
imports and
strings were
hidden in the
packed malware

35. Remember this?
Further analysis shows the binary
communicating with a Command & Control
server called brb.3dtuts.by

36. Demo

37. Conclusion

38. Thank you