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374 Chapter 14 Security engineering

Technology Choice Vulnerabilities

Users Set Authorized Users Reveal
Login/Password Guessable their Passwords to
Authentication
Passwords Unauthorised Users

Server Subject to Confidential Information
Denial of Service May be Left in Browser
Client/Server Attack Cache
Architecture Using
Web Browser Browser Security
Loopholes Lead to
Unauthorized Access

Fine-Grain Logging Authorization can’t
Figure 14.3 Use of Editable of Changes is be Varied According
Vulnerabilities Web Forms Impossible to User’s Role
associated with
technology choices

For a generic system, these design decisions are perfectly acceptable, but a life-
cycle risk analysis reveals that they have associated vulnerabilities. Examples of pos-
sible vulnerabilities are shown in Figure 14.3.
Once vulnerabilities have been identified, you then have to make a decision on
what steps that you can take to reduce the associated risks. This will often involve
making decisions about additional system security requirements or the operational
process of using the system. I don’t have space here to discuss all the requirements
that might be proposed to address the inherent vulnerabilities, but some examples of
requirements might be the following:

1. A password checker program shall be made available and shall be run daily.
User passwords that appear in the system dictionary shall be identified and users
with weak passwords reported to system administrators.
2. Access to the system shall only be allowed to client computers that have been
approved and registered with the system administrators.
3. All client computers shall have a single web browser installed as approved by
system administrators.

As an off-the-shelf system is used, it isn’t possible to include a password checker in
the application system itself, so a separate system must be used. Password checkers ana-
lyze the strength of user passwords when they are set up, and notify users if they have
chosen weak passwords. Therefore, vulnerable passwords can be identified reasonably