CheckPlease: Payload-Agnostic Targeted Malware
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CheckPlease is a tool that provides payload-agnostic checks to determine if malware is running in a targeted environment or sandbox. It evolved from signatures to behavioral detection as malware changed languages and used obfuscation. CheckPlease implements over 70 checks across multiple languages to validate processes, user behavior, system metadata and environment matches the target before executing malicious code. The presenters demonstrate various checks and encourage integrating CheckPlease with frameworks like Veil to automatically generate targeted malware payloads.
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CheckPlease: Payload-Agnostic Targeted Malware
- 1. CheckPlease - Payload-Agnostic Targeted Malware @Arvanaghi & @ChrisTruncer
- 2. Brandon Arvanaghi Associate Consultant at Mandiant Red teaming, reverse engineering, tool developer Vanderbilt University 2
- 3. Chris TruncerPrevious Sys Admin turned Red Team West Coast Red Team Lead Open Source Developer Veil, EyeWitness, WMImplant 3
- 4. What’s this talk about? ▰ Evolution of antivirus ▰ A shift to behavioral detection ▰ Introduction to CheckPlease ▰ Walkthrough of various checks ▰ Use today :) ▰ Questions 4
- 5. Why? We are not delivering ransomware. 5
- 6. Antivirus Evolution From then to now 6 #avlol
- 7. AV Detection Methods ▰ Antivirus has existed for quite some time ▰ AV companies tried to solve the malware problem with writing signatures ▻ Probably didn’t anticipate the cat and mouse game ▰ Static signatures were effective ▻ For about 5 minutes 7
- 8. AV Detection Methods ▰ Automation helped, but static signature itself isn’t effective ▻ Veil, anything custom, any other project beats this ▰ Behavioral based detection came next ▻ What can a machine “observe” about malware? 8
- 9. AV Detection Methods ▰ Behavioral based detection watches: ▻ Network traffic ▻ File creation/deletion ▻ Registry modifications ▻ Created/Killed processes ▻ etc. 9
- 10. AV Detection Methods ▰ Over time, AV started getting better at reviewing malware written in “traditional” languages ▻ C, C++, C# ▰ These were the languages they primarily saw, so they had to build out this capability 10
- 11. And then… there were new methods ▰ However… malware started to be developed in non-standard languages ▻ Python ▻ Ruby ▻ Go ▻ PowerShell ▻ Perl ▰ But why? 11
- 12. 12
- 13. 13
- 14. 14 Simply changing the language the code is written in completely bypassed all signatures.
- 15. Cat and Mouse ▰ This is really similar to where we are today, a game of cat and mouse ▻ Attackers strike, defenders detect, attackers mod… goto one ▰ Signatures leads to new obfuscation ▰ Obfuscation leads to new signatures 15
- 16. A Decent Approach ▰ So let’s focus on dynamic analysis ▰ This is just the best way to do it right? Since it sees everything. 16
- 17. The New Battleground ▰ Dynamic analysis is the new cat and mouse battleground ▰ Malware developers attempt to check and see if they are on the targeted system, or in a sandboxed environment prior to malicious execution ▻ If in a sandbox, just do some math and that’s it ▰ So, where do we go from here? 17
- 18. Our Philosophy ▰ Fighting against static detection is the old school cool ▰ Now, it’s even more important to write code that runs on your target, and that alone ▻ The new cat and mouse! 18
- 19. CheckPlease 19
- 20. Languages Supported ▰ C ▰ C# ▰ PowerShell ▰ Python ▰ Go ▰ Ruby ▰ Perl 20
- 21. CheckPlease 21
- 22. CheckPlease ▰ Easily add new detection techniques ▰ Search the technique you want, choose from the implementations ▻ Stack ‘em 22
- 23. Why multiple languages? ▰ Uptick in payload deliverance ▰ One language may not be caught ▰ Targeting malware per system ▰ Allows sandbox, AV vendors to better defend 23
- 24. CheckPlease ▰ So, we’ve talked about this a lot, but what is CheckPlease actually doing? ▰ Let’s talk techniques 24
- 25. Daddy Issues 25
- 26. Parent Process ▰ Every time we launch a payload, we know exactly what the parent process should be! ▻ Word document? ▻ PDF document? ▻ HTA application? ▰ But we won’t know the ppid ▻ What most languages support finding 26
- 30. Payload Sleeping ▰ This is what a lot of people try first ▰ Make your payload sleep an hour ▻ No sandbox would observe for an hour ▻ Resources aren’t infinite ▰ Should work right? ▻ Wrong 30
- 31. Payload Sleeping ▰ Sandbox devs know this too ▻ They will look for sleep calls in a payload, and hook them ▻ Sleep calls can be fast-forwarded ▻ Next steps will be immediately executed ▰ So… how to beat this? 31
- 32. Payload Sleeping ▰ Outsource the time validation with NTP servers ▻ Make a request to a NTP server for current time ▻ Attempt to sleep for attacker-defined period ▻ Make another request for time from NTP server 32
- 33. Payload Sleeping ▰ Now, just compare the two times! ▻ If we expect our malware to sleep for 30 seconds, did it? ▻ If so, then maybe we’re not in a sandbox! ▻ If not, then it’s highly likely we are in a sandbox :( 33
- 34. Payload Sleeping ▰ If the payload thinks it is in a sandbox, then do something innocuous and exit ▰ Otherwise, run the rest of your code! 34
- 35. Payload Sleeping ▰ Alternative Option? ▻ Create functions that can reliably take a select period of time ▻ Use those to avoid any sleep calls 35
- 37. User Interaction We all love users :) 37
- 38. Working with Users ▰ What’s normal activity on user workstations? ▻ Users browsing web pages ▻ Files in certain folders ▻ Using a mouse to navigate their workstation 38
- 39. Working with Users ▰ So let’s take normal activity, and make “indicators of users” for them ▰ We want to validate evidence of normal user activity vs. a system designed to run an unknown file 39
- 40. What should we look for? ▰ Mouse Clicks! ▻ These can be a decent indicator of user activity ▰ Specify a minimum number of clicks before executing the payload 40
- 42. What should we look for? Mouse Position ▰ Mouse Position! ▻ You move your mouse from time to time, don’t you? ▻ Sandboxes might not. ▻ Check the x and y coordinates of the mouse, wait, then check again 42
- 44. What should we look for? ▰ Web Browsers! ▻ How many web browsers do people normally have? ▻ Internet Explorer ▻ Edge ▻ Chrome? ▻ Check the number of browsers 44
- 46. What should we look for? ▰ What about USB drives? ▻ Likely that most people have used USB drives on their system ▻ Make a check for the number of USB drives in a computer 46
- 47. Ruby: USB Device History 47
- 49. Targeted Code ▰ We’ve looked at: ▻ Programmatic bypasses ▻ User behavior ▰ Now, let’s look at host machine metadata 49
- 50. Targeted Code ▰ Why make malware very targeted? It stops the spread! ▻ Well, that’s one benefit ▻ If we’re not specifically on the host we’re targeting, ideally it won’t run ▻ Sandbox may not be able to trigger the malicious code ▰ Phish for information about your targets! 50
- 51. Targeted Code - Dlls ▰ Check for known sandbox dlls ▻ There’s a bunch of dlls that we can search for ▻ Vmcheck.dll ▻ Wpespy.dll ▻ Many more... ▻ If we find one, it might be on a system we don’t want to run our code 51
- 52. Targeted Code - Dlls 52
- 53. Targeted Code - MAC ▰ MAC Addresses are easy to obtain ▰ Enumerate the MAC address of the local system ▰ Write code that only runs on a system with a specific payload 53
- 54. Targeted Code - MAC 54
- 55. Targeted Code - UTC Time Zone ▰ What time zone do you expect the targeted system to use? ▰ UTC may be used by various sandboxes ▰ Check to make sure our code isn’t running in a system using UTC 55
- 56. Targeted Code - UTC Time Zone 56
- 57. Targeted Code - Process Names ▰ We can write code that easily enumerates currently running processes on the system ▰ Why not check for processes we don’t running while our own code is? ▻ Wireshark ▻ Vmware ▻ Process Explorer ▻ tcpview 57
- 58. Targeted Code - Process Names 58
- 59. Targeted Code - Disk Space ▰ You can reasonably assume that modern computer systems have a large amount of hard drive space ▻ At least 50? ▻ At least 100? ▻ At least 250? ▰ Validate your best guess! 59
- 60. Targeted Code - Disk Space 60
- 61. Windows Updates ▰ Number of installed Windows updates can tell you about… ▻ Computer usage ▻ How often computer is restarted ▰ A real user updates more often than a poser 61
- 63. Registry Size ▰ Do you know the rough size of the registry on your system? ▻ We have a decent idea of where the size should be ▻ Compare these sizes! 63
- 64. Registry Size 64
- 65. CheckPlease ▰ There’s many more checks available: ▻ Domain Name ▻ System Hostname ▻ Anti-Debug ▻ FilePath Existence ▻ Registry Keys ▻ RAM size ▻ ...and many more 65
- 66. CheckPlease - The Point ▰ You can take any one of these checks, or chain multiple together ▻ Make all checks pass in order for your code to run ▻ If one fails, just be a simple calculator :) 66
- 67. CheckPlease - The Point ▰ Environment enumeration and help determine if it is “safe” ▰ We’ve curated a large collection of checks that can perform enumeration ▰ Just plug in what you want to search for, and verify your environment! 67
- 68. CheckPlease & Veil ▰ This is a great opportunity to help Veil’s codebase ▰ It allows users to take these checks and instantly create targeted stagers ▰ Merge this code base into Veil! 68
- 69. CheckPlease ▰ CheckPlease is now available online ▻ https://github.com/Arvanaghi/CheckPlease 69