Distributed Computer Security

1. Distributed Computer Security 8320 Advanced Operating Systems - Section 8.1 Qiong Cheng Fall 2007

2. Outline • Characteristics in Robust Systems • Security Threats • Examples: Denial-of-Service • Layered Approach for Defense • Security Policy, Mechanism and Model • Example: Enterprise Access Security Architecture • Security Issues in Distributed Systems

3. Distributed Computer Security • Security and Fault Tolerance • Robust System • Secrecy Protection from unauthorized disclosure of system objects • Integrity Only authorized users modify system objects • Availability Authorized users are not prevented from accessing respective objects • Reliability and Safety are fault-tolerant features

4. Security Threats • Interruption (availability) • Loss of data and denial of service • Interception • Related to secrecy • Modification and Fabrication are violations of system integrity

5. Threats from Web/Network • Client Side • What can the server do to the client? • Fool it • Install or run unauthorized software, inspect/alter files • Server Side • What can the client do to the server? • Bring it down (denial of service) • Gain access (break-in) • Network • Is anyone listening? (Sniffing) • Is the information genuine? Are the parties genuine? Source : www.cse.sc.edu/~farkas/csce522-2003/lectures/csce522-lect22.ppt

6. Packet Sniffing (Network threat) EVERY NETWORK INTERFACE CARD HAS A UNIQUE 48-BIT MEDIA ACCESS CONTROL (MAC) ADDRESS, e.g. 00:0D:84:F6:3A:10 24 BITS ASSIGNED BY IEEE; 24 BY CARD VENDOR Packet Sniffer Server Client NETWORK INTERFACE CARD ALLOWS ONLY PACKETS FOR THIS MAC ADDRESS PACKET SNIFFER SETS HIS CARD TO PROMISCUOUS MODE TO ALLOW ALL PACKETS THROUGH

7. Network Security Problem REMOVABLE MEDIA REMOTE LOCATION USER MODEM + TELEPHONE “BACKDOOR” INTERNET CONNECTION RADIO EMISSIONS LOCAL AREA NETWORK WIRELESS USER INTERNET CONNECTION ISP REMOTEUSER VENDORS AND SUBCONTRACTORS SOURCE: CERT

8. Sophistication v. Intruder Knowledge SOURCE: CERT

9. Denial-of-Service • Attack to disable a machine (server) by making it unable to respond to requests • Use up resources • Bandwidth, swap space, RAM, hard disk • Some attacks yield millions of service requests per second

10. Internet Ping Flooding Attacking System(s) Victim System SOURCE: PETER SHIPLEY

11. SYN ACK Server SYN | ACK Client Three-Way Handshake 1: Send SYN seq=x 2: Send SYN seq=y, ACK x+1 3: Send ACK y+1 SOURCE: PETER SHIPLEY

12. 1 SYN 10,000 SYN/ACKs -- VICTIM IS DEAD SMURF ATTACK INTERNET PERPETRATOR VICTIM INNOCENTREFLECTOR SITES BANDWIDTH MULTIPLICATION: A T1 (1.54 Mbps) can easily yield 100 MBbps of attack ICMP echo (spoofed source address of victim) Sent to IP broadcast address ICMP echo reply ICMP = Internet Control Message Protocol SOURCE: CISCO

13. Distributed Denial of Service Attack INTRUDER SENDS COMMANDS TO HANDLERS INTRDER VICTIM SOURCE: CERT

14. DDOS Attack SOURCE: CERT

15. DDOS Attack SOURCE: CERT

16. Strong passwords, ACLs, backup and restore strategy Policies, procedures, and awareness Physical security Data Application Application hardening OS hardening, authentication, security update management, antivirus updates, auditing Host Internal network Network segments, NIDS Firewalls, boarder routers, VPNs with quarantine procedures Perimeter Guards, locks, tracking devices Security policies, procedures, and education A Layered Approach for Defense • Increases an attacker’s risk of detection • Reduces an attacker’s chance of success

17. Security Policy • Access Control Policy • Describes how objects are accessed by subjects • Flow Control Policy • Regulates the information flow between objects and subjects • Subjects • Active entities that access objects • Objects • Passive entities that must be protected • Examples: data, hardware, software and communication links

18. Security Mechanism • Authentication • Verification • Authorization • Extending permission • Fault Tolerance • Sustaining faults • Encryption • Prevents exposure of information and maintains privacy • Auditing • Passive form of protection

19. Security Model • Discretionary • Provides separation of users and data • E.g. access control matrix • Mandatory • Requires access control of all subjects and orders under its control on a system wide basis • E.g. multilevel security, all subjects and objects in the system are assigned a sensitivity label. The labels are used as the basis for mandatory access control decisions.

20. Firewall • A device placed between two networks or machines • All traffic in and out must pass through the firewall • Only authorized traffic is allowed to pass • The firewall itself is immune to penetration Company Network Firewall Internet SOURCE: ADAM COLDWELL

21. Internet Access Authentication Server Internet RSA Agent RSA Agent RSA Agent Remote Access Enterprise Access Security Enterprise Access RSA Agents Mainframe Web Server Firewall Enterprise Intranet UNIX RAS SOURCE: RSA

22. Security Issues in Distributed Systems • Interoperability and Transparency • Gives rise to security issues • Approaches to Implementing New Services • Add an additional layer of software that runs on top of the existing system to provide the new services • Redesign the system so that the new services can be executed more efficiently in the kernel mode

23. Strong passwords, ACLs, backup and restore strategy Policies, procedures, and awareness Physical security Data Application Application hardening OS hardening, authentication, security update management, antivirus updates, auditing Host Internal network Network segments, NIDS Firewalls, boarder routers, VPNs with quarantine procedures Perimeter Guards, locks, tracking devices Security policies, procedures, and education Comprehensive Consideration

24. References 1.http://www.owasp.org/index.php/Top_10_2007 2. www.cert.org 3. www.cse.sc.edu/~farkas/csce522-2003/lectures/csce522-lect22.ppt 4. Randy Chow, Theodore Jognson. Distributed Operating Systems and Algorithms, Addison-Wesley 1997