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Nick Guo , Ulysses Wang

JavaScript De-Obfuscation Engine -- JDOE. Nick Guo , Ulysses Wang. Agenda. Obfuscation Introduction Anti de-obfuscation Browser Knowledge Current Solution JDOE Demo Challenge & Improvement. Obfuscation Introduction. Phase I Review. Obfuscation.

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Nick Guo , Ulysses Wang

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  1. JavaScript De-Obfuscation Engine -- JDOE Nick Guo, Ulysses Wang

  2. Agenda • Obfuscation Introduction • Anti de-obfuscation • Browser Knowledge • Current Solution • JDOE • Demo • Challenge & Improvement

  3. Obfuscation Introduction Phase I Review

  4. Obfuscation • Concealing the intent of the code by making the code difficult for human analysis and detection • Copy right protection • Hide Information (E.g. Email address) • Evade detection

  5. Obfuscation Types • Three types of obfuscations • Injection obfuscation • Public Packer Obfuscation • Exploit Kit Obfuscation

  6. Obfuscation Types • “As recorded in 2007, over 80% of detected malicious code was already using obfuscation” • Most obfuscations are simple. • Injection: 83%, exploit kit: <1% • Complex obfuscations occupy a small proportion. • Obfuscation become more complex

  7. Anti de-obfuscation JDOE Prototype

  8. Fragmentation • Splitting important codes into pieces of Javascirpt code, HTML code or external scripts • String concatenate • Var temp=“get”+”Elem”+”ent”+”ById” • Tag concatenate • Put content in <div>,<p>,<textarea> • OpenSource Exploit kit

  9. Fragmentation • File concatenate • Put critical function or data in another file • Phoenix Exploit Kit 2.5 • Traffic concatenate • Save data on server and client need to request

  10. External Access • Fetch external access or perform a connection check • Ajax fetch data • Connection check • Neosploit exploit kit

  11. Condition check • Browser detect uas=navigator.userAgent; while(uai<uas.length) {xor+=uas.charCodeAt(uai++);} • IE6 • Firefox

  12. Condition check • Time check • getUTCFullYear() • getUTCMonth() • getUTCDate() • Plugin check • newActiveXObject('ShockwaveFlash.ShockwaveFlash'); (IE) • Check navigator.plugins (not IE)

  13. Trigger Function • Trigger a function after certain seconds • setTimeout("alert(Hello!')",3000) • setInterval("clock()",1000) • Trigger a function on certain event • <body onload="load()"> • <button id="j_id" onclick="j_function2();" • window.attachEvent or addEventListener • Trigger a function on plugin • Call js function from Actionscript

  14. Bypass de-obfuscation tool • Uncommon tag • Save content in CSS • Modification check • varhybxs = arguments.callee;hybxs = hybxs.toString();

  15. Browser Knowledge JDOE Prototype

  16. Browser Component

  17. Webkit

  18. DOM Tree

  19. Current Solution Phase I Review

  20. Jsunpack • Light weight • Spidermonkey and Python • Set hook in js file • Environment DOM Enumeration • Detection module(Yara) • PDF and SWF parser • Intrusion Detection(libnids) • http://jsunpack.jeek.org/

  21. Fireshark • Firefox Plugin • Mainwindow and child Frame Source Code • Mainwindow and child Frame DOM Tree • Http Request and Response Logged • Malicious URL check • URL redirection graph • http://fireshark.org/

  22. Malzilla • Research tool • Spidermonkey • Shellcode analysis • Limited DOM support • http://malzilla.sourceforge.net/

  23. Limitations • Firefox based • Limited on DOM support • Limited on De-obfuscation • Performance

  24. JDOE Phase I Review

  25. JDOE • What engine we want ? • High performance • Good coverage • Good output and log formats • Analytics platform

  26. JDOE • JDOE is based on Google Chrome • Render Engine : Webkit • 85% smart phone browser market • 21% desktop browser market • Include DOM tree and parser • JavaScript Engine : V8

  27. Prototyping • JDOE based on a test project for Chrome • Command line tool, feasible to be ported as server-side application • Be able to simulate basic functions of browser • Full DOM Support • Good fault tolerance about html format • HTML format output

  28. JDOE Architecture

  29. JDOE advantage • Base on Chrome and Webkit • Strong Parser • Full DOM Support • Fast js execution speed • High coverage • Good expansibility

  30. De-obfuscation Method • JDOE De-obfuscation Method • Hook eval() • Get some inner status of JavaScript • Print the final DOM tree • Get the final status • Document.write should add some nodes in DOM tree

  31. Exploit kit Coverage • Exploit kits Samples • Samples from Top 10 exploit kits project • Total Samples : 22 JDOE success : 20 • Coverage : 90.9%

  32. Injection Coverage • Injection Samples • Samples from obfuscation ThreatID matches • Total Samples : 9,544 JDOE Success : 8,450 • Coverage : 88.5%

  33. Demo time Demo

  34. Challenge & Improvement Status and Next Step

  35. Challenge • Security • How to keep JDOE server secure? • Upgrade plan • Sandbox • Javascript Audit • Performance • Disable external access • Coverage • Not support on special samples • Output format defected on special samples

  36. improvement • More trigger function handler • PDF and SWF Parser • Shellcode detection • JavascriptAudit • Cloud base integration • http://aceinsight.websense.com/ • Auto analysis platform

  37. JDOE Questions?

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