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Security “Tidbits”

Security “Tidbits”. Neil Daswani. Overview. The FLI Model Infiltrations: Viruses / Worms Lessons Learned Firewalls & Attacks What is a firewall? How do they work? How to prevent attacks. Failure (Process/Storage). Lies. Infiltration. Prevention. Physical Security

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Security “Tidbits”

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  1. Security “Tidbits” Neil Daswani

  2. Overview • The FLI Model • Infiltrations: • Viruses / Worms • Lessons Learned • Firewalls & Attacks • What is a firewall? • How do they work? • How to prevent attacks

  3. Failure (Process/Storage) Lies Infiltration Prevention Physical Security Uninterruptible Power Firewalls Authentication Authorization Non-Repudiation Time-Stamping Digital Signatures Hardware Protection Firewalls “Common Sense”  Management Non-Stop Processes Fault-Tolerance Watchdog Processor Replication, RAID Backups Byzantine Agreement Reputation Systems Intrusion Detection Anti-virus Software Recovery Fail-Over Hot Swapping Key Escrow Fail-Stop Digital Signatures Auditing Certificate Revocation Security Problems & Solutions

  4. Morris Worm (1988) • Damage: 6000 computers in just a few hours • What: just copied itself; didn’t touch data • Exploited: • buffer overflow in fingerd (UNIX) • sendmail debug mode (exec arbitrary cmds) • dictionary of 432 frequently used passwords

  5. Buffer Overflow Example void sample_func (char *str) { char buffer[16]; strcpy (buffer, str); } void main (int argc, char *argv) { sample_func (argv[1]); }

  6. Morris Worm (1988) • Lessons Learned from Morris • Diversity is good. • Big programs have many exploitable bugs. • Choose good passwords. • Don’t shut down mail servers: did prevent worm from spreading but also shut down defense • CERT was created to respond to attacks

  7. Melissa (1999) • What: just copied itself; did not touch data • When date=time, “Twenty-two points, plus triple word score, plus fifty points for using all my letters. Game’s over. I’m outta here.” • Exploited: • MS Word Macros (VB) • MS Outlook Address Book (Fanout = 50)“Important message from <user name> …”

  8. Melissa (1999) • Lessons Learned: • Homogeneity is bad. • Users will click on anything. • Separation of applications is good. • Users “trusted” the message since it came from someone they knew. • Don’t open attachments unless they are expected.

  9. Other Viruses / Worms • CIH Chernobyl Virus, 1998, Taiwan: • Time bomb: April 26, or 26th of each month • Writes random garbage to disk start at sector 0 • attempts to trash FLASH BIOS • Hides itself in unused spaces • Worm.ExploreZip, 1999: Melissa + zeroed out files • BubbleBoy, 1999: Melissa-like except doesn’t require opening an attachment (ActiveX) • Love Bug, 2000: “I LOVE YOU” (like Melissa)

  10. Code Red (2001) • Runs on WinNT 4.0 or Windows 2000 • Scans port 80 on up to 100 random IP addresses • Resides only in RAM; no files • Exploits buffer overflow in Microsoft IIS 4.0/5.0(Virus appeared one month after advisory went out) • Two flavors: • Code Red I: high traffic, web defacements, DDOS on whitehouse.gov, crash systems • Code Red II: high traffic, backdoor install, crash systems • Three phases: propagation (1-19), flood (20-27), termination (28-31) • Other victims: Cisco 600 Routers, HP JetDirect Printers

  11. Code Red (2001) • Lessons Learned: • Don’t use IIS! ;) • Always keep software up-to-date • Proof-of-concept to hide other attacks?

  12. Nimda (2001) • Multiple methods of spreading(email, client-to-server, server-to-client, network sharing) • Server-to-client: IE auto-executes readme.eml (that is attached to all HTML files the server sends back to the client) • Client-to-server: “burrows”: scanning is local 75% of time • Email: readme.exe is auto executed upon viewing HTML email on IE 5.1 or earlier

  13. Nimda (2001) • Lessons Learned: • Install latest web server and browser patches (or upgrade version altogether) • Don’t use MIME auto-execution • Disable JavaScript • Reject using applications that are routinely exploited???

  14. Just this week… BadTrans Worm • Spread via email; attacks Windows systems • Records (once per second) keystrokes, usernames, & passwords into windows with titles: LOG, PAS, REM, CON, TER, NET • Sends to • one of 20+ email addresses • one of 15+ from addresses • one of 15+ attachment names w/ 2 extensions ({.doc/.mp3/.zip},{.pif/.scr})

  15. Firewalls • Two major technologies: • Packet Filters • Proxies • Related technologies • Network Address Translation (NAT) • Virtual Private Networks (VPN)

  16. Packet Filtering Routers • Filter on: • IP Source, IP Dest, Protocol (TCP, UDP, ICMP) • TCP/UDP Source & Dest Ports • ICMP Message Type (req,reply,time exceed) • Packet Size • NICs • Stateful vs. Stateless Inspection • i.e., UDP DA/DP checking • Simple Protocol Checking • i.e., Format Checking, Disconnect “anonymous” FTP x-fers

  17. Packet Filtering • Advantages • One router can protect entire network • Simple filtering is efficient • Widely available • Disadvantages • Hard to configure & test • Reduces router performance • Can’t enforce some policies (i.e., user-level)

  18. Proxies • Security vs. Caching Proxies • SOCKS: proxy construction toolkit • Trusted Information Systems Firewall Toolkit (TIS FWTK: Telnet, FTP, HTTP, rlogin, X11) • Most used to control use of outbound services • Can also be used to control inbound services (reverse proxying)

  19. Proxies • Advantages • Logging, Caching, Intelligent Filtering • User-level authentication • Guards against weak IP implementations • Disadvantages • Lag behind nonproxied services • Requires different servers for each service • Usually requires modifications to client applications

  20. Firewall Architectures • Dual-Homed Host • Services can only be proxied • Screening Router w/ Bastion Host • Security by packet filtering • Bastion host is single point of failure • Screened Subnet • Ext Router, Perimeter, Bastion Host, Interior Router • Internal ethernet packets protected from perimeter

  21. Example Attacks • IP Spoofing • TCP SYN Flood • SMURF Attack • ICMP Ping w/ max payload to broadcast address • D-DOS Attack • Infiltrate, set up sleepers, attack at once

  22. References • White-Hat Security Arsenal, A. Rubin • Security Engineering, R. Anderson • www.webtorials.com, Gary Kessler • Building Internet Firewalls, E. Zwicky, et. Al. • Counter Hack, E. Skoudis

  23. Network Address Translation (NAT) • Translates network addresses & ports • Does not provide additional “security” • Possibilities: • One external address per internal address • Dynamically assign external address • Map multiple internal to one external (port sharing) • Dynamically assign external addresses and ports

  24. Network Address Translation (NAT) • Advantages • Helps enforce control over outbound connections • Helps restrict incoming traffic • Helps conceal internal network configuration • Disadvantages • Not good for UDP (guess session lifetimes) • Doesn’t deal with embedded IP addresses • Interferes with authentication & encryption • Interferes with logging & packet filtering

  25. Virtual Private Networks • Advantages: • Provides overall encryption • Allows use of protocols that are hard to secure any other way • Disadvantages: • Involves “dangerous” network connections • Extends the network that must be protected

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