Uses of E-mail

•Anonymity allowed

–Exception: if it violates laws or other policies

•Can’t interfere with others’ use of e-mail

–No spam, letter bombs, e-mailed worms, etc.

•Personal e-mail allowed within limits

–Cannot interfere with university business

–Such e-mail may be a “university record” subject to disclosure

Security of E-mail

•University can read e-mail

–Won’t go out of its way to do so

–Allowed for legitimate business purposes

–Allowed to keep e-mail robust, reliable

•Archiving and retention allowed

–May be able to recover e-mail from end system (backed up, for example)

Implementation

•Adds campus-specific requirements and procedures

–Example: “incidental personal use” not allowed if it benefits a non-university organization

–Allows implementation to take into account differences between campuses, such as self-governance by Academic Senate

•Procedures for inspecting, monitoring, disclosing e-mail contents

Backups

Summary

•Warns that electronic mail not private

–Can be read during normal system administration

–Can be forged, altered, and forwarded

•Unusual because the policy alerts users to the threats

–Usually, policies say how to prevent problems, but do not define the threats

•What users should and should not do

–Think before you send

–Be courteous, respectful of others

–Don’t nterfere with others’ use of email

•Personal use okay, provided overhead minimal

•Who it applies to

–Problem is UC is quasi-governmental, so is bound by rules that private companies may not be

–Educational mission also affects application

Full Policy

•Context

–Does not apply to Dept. of Energy labs run by the university

–Does not apply to printed copies of email

•Other policies apply here

•E-mail, infrastructure are university property

–Principles of academic freedom, freedom of speech apply

–Access without user’s permission requires approval of vice chancellor of campus or vice president of UC

–If infeasible, must get permission retroactively

Mechanisms

•Entity or procedure that enforces some part of the security policy

–Access controls (like bits to prevent someone from reading a homework file)

–Disallowing people from bringing CDs and floppy disks into a computer facility to control what is placed on systems

Example English Policy

•Computer security policy for academic institution

–Institution has multiple campuses, administered from central office

–Each campus has its own administration, and unique aspects and needs

•Authorized Use Policy

•Electronic Mail Policy

Authorized Use Policy

•Intended for one campus (Davis) only

•Goals of campus computing

–Underlying intent

•Procedural enforcement mechanisms

–Warnings

–Denial of computer access

–Disciplinary action up to and including expulsion

•Written informally, aimed at user community

Electronic Mail Policy

•Systemwide, not just one campus

•Three parts

–Summary

–Full policy

–Interpretation at the campus

Trust

Administrator installs patch

1.Trusts patch came from vendor, not tampered with in transit

2.Trusts vendor tested patch thoroughly

3.Trusts vendor’s test environment corresponds to local environment

4.Trusts patch is installed correctly

Trust in Formal Verification

•Gives formal mathematical proof that given input i, program P produces output o as specified

•Suppose a security-related program S formally verified to work with operating system O

•What are the assumptions?

Trust in Formal Methods

1.Proof has no errors

•Bugs in automated theorem provers

2.Preconditions hold in environment in which S is to be used

3.S transformed into executable S¢ whose actions follow source code

–Compiler bugs, linker/loader/library problems

4.Hardware executes S¢ as intended

–Hardware bugs (Pentium f00f bug, for example)

Security Policies

•Policy partitions system states into:

–Authorized (secure)

•These are states the system can enter

–Unauthorized (nonsecure)

•If the system enters any of these states, it’s a security violation

•Secure system

–Starts in authorized state

–Never enters unauthorized state

Confidentiality

•X set of entities, I information

•I has confidentiality property with respect to X if no x Î X can obtain information from I

•I can be disclosed to others

•Example:

–X set of students

–I final exam answer key

–I is confidential with respect to X if students cannot obtain final exam answer key

Computer Security

Trust and Assumptions

•Underlie all aspects of security

•Policies

–Unambiguously partition system states

–Correctly capture security requirements

•Mechanisms

–Assumed to enforce policy

–Support mechanisms work correctly

Assurance

•Specification

–Requirements analysis

–Statement of desired functionality

•Design

–How system will meet specification

•Implementation

–Programs/systems that carry out design

Computer Security

Basic Components

Confidentiality

–Keeping data and resources hidden

•Integrity

–Data integrity (integrity)

–Origin integrity (authentication)

•Availability

–Enabling access to data and resources

Classes of Threats

Disclosure

–Snooping

•Deception

–Modification, spoofing, repudiation of origin, denial of receipt

•Disruption

–Modification

•Usurpation

–Modification, spoofing, delay, denial of service