Electronic Commerce - Chapter 6: System securityt - Tran Thi Que Nguyet

Nội dung text: Electronic Commerce - Chapter 6: System securityt - Tran Thi Que Nguyet

1. Electronic Commerce Chapter 6: System security Email: ttqnguyet@hcmut.edu.vn
2. Security requirements • Confidentiality • Integrity • Availability • Non-repudiation
3. Security threats • Type of threats • Disclosure: unauthorized access to information • Deception: acceptance of false data • Disruption: interruption or prevention of correct operation • Usurpation: unauthorized control of some part of a system • The security life cycle
4. Common attacks • Masquerading (or spoofing): impersonation of one entity by another, is a form of deception, and usurpation • Passive or active • Repudiation of origin: false denial that an entity sent something, is a form of deception • Active • Denial of service: long-term inhibition of service, is a form of usurpation • Active • May happen at the source, the destination, or the communication path
5. Common attacks • Computer virus: is a program that inserts itself into one or more files and then performs some actions • A boot sector infector is a virus that inserts itself into the boot sector of a disk • An executable infector is a virus that infects executable programs • An encrypted virus is one that enciphers all of the virus code except for a small decryption routine • A polymorphic virus is a virus that changes its form each time it inserts itself into another program • A macro virus is a virus composed of a sequence of instructions that is interpreted, rather than executed directly
6. Authentication • Authentication is the process of verifying the identity a subject claims it to be • The subject must provide information to enable the system to confirm its identity • Something the subject knows • Something the subject has • Something the subject is • Combination of them • Authentication mechanism • Password • Challenge-response • Biometrics • Multi-factor
7. Authentication • Defending the password system • Users need to use “good” password • Theorem: let the expected time required to guess a password be T, then T is maximum when the selection of any of a set of possible passwords is equals • Random computer-generated passwords: strong, but difficult for human users • Pronounceable computer-generated passwords: compromise between passwords selected by users and generated by computer randomly • Password aging: a password must be changed after some period of time or after some event has occurred
8. Authentication • Challenge-response example: CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) • Challenge-response authentication (that you are human) • What is challenge, what is response? • Easy for authenticated subjects (human) but difficult for unauthenticated ones: is that assumption still valid now?
9. Authentication • Biometrics • The automated measurement of biological or behavioral features that identify a person • Based on “something the subject is” • Many features can be used • Fingerprints • Voice • Face • Keystroke • Gesture • Problems • Noisy data • Not easy to change once be stolen • Availability
10. Access control • Access control: exerting control over who can interact with a resource • Types of access control • Discretionary access control (DAC): a subject with a certain access permission is capable of passing that permission on to any other subject • Mandatory access control: the operating system constrains the ability of a subject to access an object • Access control presentation • Access control matrix • Objects: columns • Subjects: rows • Access permission: respected cells
11. Access control • Bell-LaPadula model • Subjects have security clearance: TS (top secret), S (secret), C (confidential), UC (unclassified) (ls) • Object have security classification: the same as above (lo) • Simple security condition: subject can read object if and only if lo <= ls • Star property: subject can write to object if and only if ls <= lo