Sommerville-Software-Engineering-10ed

13.4 ■ Secure systems design 391
Technology choice
Vulnerabilities
Login/password
authentication
Users set
guessable
passwords
Authorized users reveal
their passwords to
unauthorized users
Client/server
architecture using
web browser
Server subject to
denial-of-service
attack
Confidential information
may be left in browser
cache
Browser security
loopholes lead to
unauthorized access
Figure 13.12
Vulnerabilities
associated with
technology choices
Use of editable
web forms
Fine-grain logging
of changes is
impossible
Authorization can’t be
varied according to user’s
role
To illustrate how decisions on development technologies influence security,
assume that the health care provider has decided to build a Mentcare system using an
off-the-shelf information system for maintaining patient records. This system has to
be configured for each type of clinic in which it is used. This decision has been made
because it appears to offer the most extensive functionality for the lowest development
cost and fastest deployment time.
When you develop an application by reusing an existing system, you have to
accept the design decisions made by the developers of that system. Let us assume
that some of these design decisions are:
1. System users are authenticated using a login name/password combination. No
other authentication method is supported.
2. The system architecture is client–server, with clients accessing data through a
standard web browser on a client computer.
3. Information is presented to users as an editable web form. They can change
information in place and upload the revised information to the server.
For a generic system, these design decisions are perfectly acceptable, but design
risk assessment shows that they have associated vulnerabilities. Examples of these
possible vulnerabilities are shown in Figure 13.12.
Once vulnerabilities have been identified, you then have to decide what steps you
can take to reduce the associated risks. This will often involve making decisions