Web Shell 101 Joe Schottman InfoSeCon 2018 Oct. 26, 2018 About Me Senior Security Analyst for BB&T Legal Stuff 2 How To Reach Me @JoeSchottman on Twitter [email protected] www.joeschottman.com Add me on LinkedIn Find me on local Slacks 3 Agenda What is a Web Shell? How do Web Shells work? How can you detect them? Not going to cover how to use them 4 Definitions for this talk 5 If you’re playing security conference bingo 6 First, a diversion Equifax hack ▪ ▪ ▪ 8 Equifax hack 9 Equifax hack 10 Equifax hack 11 “ 12 “ 13 What is a Web Shell? 14 A subset of malware that runs on web servers 15 Used by APT groups 16 But also script kiddies 17 Someone else’s code ▪ PHP ▪ JSP ▪ Perl ▪ Ruby ▪ Python ▪ Shell Scripts ▪ ASP 18 Mostly scripting languages 19 Designed to control your server via HTTP 20 Imagine an evil web application 21 Executes just like your web applications 22 Unless the attacker takes steps to avoid it... 23 Used for different purposes 24 Hidden in different ways 25 How do they get on systems? 26 Web Shells are not the initial attack 27 Why at least two problems? ▪ ▪ ▪ 28 Let’s consider where in the attack Web Shells are used ▪ ▪ 29 Cyber Kill Chain 30 ATT&CK Discovery Lateral movement Collection Exfiltration Command and control 31 ATT&CK 32 Time to engage incident response ▪ ▪ ▪ 33 A funny aside 34 Metasploit makes some Web Shells easy 35 Detecting Web Shells Strategies 38 39 You do get permission before doing research, right? VirusTotal 41 File integrity monitoring 42 In an ideal world... ▪ ▪ ▪ 43 Also in an ideal world... 44 Conduct tests - put new files on your web servers and see how long detection takes. File system techniques 46 Slide on YARA here 47 Dirty Word List 48 Look for encoded or encrypted content 49 Don’t forget the database 50 Log Files 51 Log Files 52 Log Files 53 Network analysis 54 Endpoint anomaly detection 55 THANKS! 56 CREDITS ▪ ▪ 57 PRESENTATION DESIGN ▪ Dosis ▪ Titillium Web #d3ebd5 · #80bfb7 · #0b87a1 · #01597f · #003b55 58.