Metasploit Framework Executable Encoding
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Metasploit Framework Executable Encoding

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A school project. How well does Metasploit encode its executables? I'm putting it to the test against 10 different antivirus programs. This is just the proposal; the finished version should be done in ...

A school project. How well does Metasploit encode its executables? I'm putting it to the test against 10 different antivirus programs. This is just the proposal; the finished version should be done in a month or so.

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Metasploit Framework Executable Encoding Metasploit Framework Executable Encoding Presentation Transcript

  • Metasploit Payload Encoding and Antivirus Detection
  • Research Question
    • How well does Metasploit’s executable encoding prevent detection by antivirus software?
  • Hypothesis & Null Hypothesis
    • Shikata na Gai encoding scheme will result in the lowest number of detections by antivirus software, because it utilizes a polymorphic engine.
    • There is no statistical difference between antivirus detection of executables that have been encoded using Metasploit
  • Introduction
    • Rationale
      • War between antivirus software and malware programmers
      • What is Metasploit?
      • How well are we protected from malware?
      • Negative affects of malware
      • Can a simple encoding scheme render AV useless?
      • What about more advanced encoders?
      • How well can AV software defend against easily accessable encoders provided by the Metasploit framwork?
  • Terms
    • Malware
      • Any file that does things to a computer that a view does not want it to, or is not aware o
    • MD5
      • Method of creating a ”fingprint” for a file. Unique to EVERY file (3.4 * 10^38 combinations possible)
    • Binary file
      • An executable program's file
    • Sandbox
      • Virtual area that is completely separated from the host computer
  • Terms Continued
    • Compile
      • To turn readable code into an executable file
    • Encryption + Decryption
      • Encryption turn information into seemingly random information, using a key (like a password). Decryption reverses this
    • Exploit
      • To take advantage of a programer's mistakes. Can make a computer execute programs. Aka- vulnerability, 0day
    • TCP/IP
      • Protocol that the Internet mainly works on
    • Virtual Machine
      • Program used to emulate (simulate) an entire computer
  • Background: How AV Works
    • 2 main methods of detection:
      • File signature
      • Heuristics
  • File Signatures
    • Most common method
    • Algorithm or static signature
      • Ex/ MD5 or look for suspitious behavior
    Person using AV to scan a file Compare signature of file to a database with known signatures Does it match the signature of a known virus? Compute a signature from the unknown file Unkown file Database of file signatures
  • File Signature Scanning
    • Benefits:
      • Easy to implement
      • Not resource intensive
    • Limitations
      • Useless against new threats
  • Heuristic Scanning Scan the file Person using AV Run it in a sandbox Monitor system calls & activity and relay info to a risk analysis engine Does it look suspicious? Unknown file Unknown file Risk analysis engine
  • Heuristic Scanning
    • Benefits:
      • Can detect new malware
      • Doesn't rely on a signature database
    • Limitations:
      • False positives
      • Resource intensive
  • How To Avoid Detection
    • Polymorphism
      • Functional portion of code is encrypted
      • Decrypted on runtime
      • Change encryption/decryption key each time run
    • Metamorphism
      • Each time malware replicates, change itself
    • Oligomorphism
      • Similar to polymorphism
      • Chooses decryptor from set of key combinations
  • Polymorphism hwfeidedwefef dfewfewfewfe grvervklmwefwe welkfimj eifcjm cwif jioregio mg wwoijmgeirojg r Encrypted portion Encryption + decryption engine with key Bla bla key=10 If (decrypted) { EvilStuff(); } Bla bla key=10 Decrypt the main code run Do evil things to the computer If (decrypted) { EvilStuff(); } Bla bla key=10 If (decrypted) { EvilStuff(); } Bla bla key=10 Change the encrytion + decryption engine, And change the key Kjlkmdckldklcm Sdclknmewnge Sdklmroivnslkw Kmewvionjrewg Wenmgrerjnkng spowgnjrekjwe Bah bah key=11 Encrypt the main code with new key and engine
  • Metamorphism 0x74 0x68 0x69 0x73 0x20 0x69 0x73 0x20 0x70 0x77 0x6e 0x7a 0x6f 0x72 0x20 0x63 0x6f 0x64 Virus (hex view) Runs and does evil stuff void main() { EvilFunction(); } void main() { EvilFunction(); UselessFunction(); } Takes its own source code and adds stuff A useless piece is added (like a NOP slide) Recompiled with new code 0x7a 0x6f 0x6d 0x67 0x20 0x64 0x69 0x73 0x20 0x69 0x00 0x00 0x00 0x00 0x00 0x73 0x20 0x6e A new binary is produced
  • Oligomorphism welkfimj eifcjm cwif jioregio mg wwoijmgeirojg r [engine] key=??? Encrypted portion Decryptor/Key Pieces If (decrypted) { EvilStuff(123); } key=a+c/b If (decrypted) { EvilStuff(321); } key=b+c^d If (decrypted) { EvilStuff(213); } key=b%2 +c A B C D
  • Metasploit Itself
    • Exploit framwork
    • Ruby
    • Exploits + payloads
    • >1mil annual downloads
    • Constantly updated with wild exploits
    • Can produce standalone trojan binaries
  • In this study...
    • Reverse TCP Payload
      • Reverse= victim connects to attacker
      • TCP= done over Internet
    • All information for connection hard encoded in executable
    Connection! Unknowing victim Evil hacker
  • Variables
    • Independent:
      • Type of encoder used
    • Dependent:
      • Whether or not the malware is detected by AV
  • Controls
    • Positive:
      • Unencoded executable
    • Negative Control:
      • A file known to be benign
      • ” hello world” program in C compiled on clean Ubuntu install
    • Constants:
      • Environment scan is performed is identical
      • Snapshot feature on Vmware
    • Same version of AV
      • All 2011
    • All AV updated to most recent virus definitions
    • Same version & installation of Metasploit used
  • Controls and More
    • Same exploit & payload
    • Same reverse TCP information (IP, port) used
    • All encodings were done on the same original executable
    • Replicates
      • Scans repeated 5 times each trial to ensure accuracy
  • Data Collection
  • Analysis
    • Is there statistical difference between encoders?
    • Chi Square Test
  • References Instruction set reference manual. (1999). Intel architecture software developer's manual . Retrieved February 3, 2011, from http://download.intel.com/design/PentiumII/manuals/24319102.PDF Glossary - securelist . (2011). Retrieved from http://www.securelist.com/en/glossary?letter=72#gloss189210535 Metasploit express user guide. (2010). Rapid7 , (3.5.1), Retrieved from www.metasploit.com/documents/express/UserGuide.pdf Metasploit framework . (2010). Retrieved from http://www.rapid7.com/products/metasploit-framework.jsp Munro, J. (2002, July 10). Antivirus research and detection techniques . Retrieved from http://www.extremetech.com/article2/0,2845,1154648,00.asp Static application data. (2008). Uninformed, 9 . Retrieved from http://uninformed.org/index.cgi?v=9&a=3&p=11