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Host and Application Security

This lesson explores the vital components of user authentication and access control in operating systems. It examines methods such as something the user knows (passwords), something they have (tokens), and something they are (biometrics). The discussion covers the importance of strong passwords, the risks of common attacks (like brute force), and strategies for secure password storage using encryption and hashing. Additionally, it addresses the use of one-time passwords and biometrics, highlighting challenges like privacy issues and false positives. The assignment prompts a comparison of Windows and Linux security.

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Host and Application Security

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Presentation Transcript

  1. Host and Application Security Lesson 8: You are you… mostly

  2. OS: If we want access control • We must have…

  3. User Authentication • Something the user knows • Something the user has • Something the user is • “Two factor” means just what it says

  4. Passwords • The most common access control paradigm • Challenges: • Loss • Convenience • Disclosure • Revocation

  5. Additional Restrictions • Time limited access • Geospatial limitations – very clever!

  6. Attacks on Passwords • Brute force • Common passwords • Likely passwords • Find the encrypted password database • Ask!

  7. Exhaustive Attack • Not as hard as one might think… • The search space is actually pretty small • How tractable is this? Very! • GPU Computing makes this very fast

  8. Probable Passwords • Lots of similarities in the way people pick passwords • Which is more likely: • Flatech or 8*fgHi@d? • Time for an xkcd…

  9. Thanks, Randall!

  10. How the Computer Stores Passwords • Cannot (should not) be stored in the clear • Encrypt them! • Originally, in the /etc/passwd file • Then, moved to /etc/shadow • Typically, we store a hash of the password • This introduces a vuln, which is…

  11. NaCl • We add a salt to each password, and store it in the clear • This is made from the process ID and the time, stored in the clear • When the password is hashed the salt is added before the hashing

  12. Spearphishing • Of course, it’s much easier to just ask the user

  13. One Time Passwords • Pretty much a challenge response • The system “asks the user a question”, usually of the form “compute this function”

  14. Biometrics • Some type of biological property • Here, though, we have to think about false positive and false negatives… • Identification versus authentication • “This is Pinkie Pie” • I am Pinkie Pie, and I present this hoof to prove it

  15. Challenges • Cost • Privacy issues • Inexact matching • Single point of failure • Token revocation (ouch!!!)

  16. The Web • How does authentication work on the web?

  17. Assignment • This is deliberately vague… • “Compare Windows and Linux security more broadly. Which is ``more secure`` and why? Justify your position.”

  18. Questions?

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