![](bg2.png)
evaluation of new security mechanisms [4]. The use of security patterns helps to
incorporate security principles when building secure systems [5]. However, they have
some limitations:
• They are small units of defense. They can only handle one (or a few) threats.
Considering the number of threats that can affect current information systems, a
security designer should tailor an extensive set of security patterns when building
secure systems.
• There are different versions of the same pattern for each architectural level. As the
building of secure systems need an extensive set of security patterns, this fact increases
the complexity when a security designer is trying to select a pattern.
• Several instantiations of a pattern may have common aspects but the designer has
to find them. This fact may cause unnecessary redundancies.
Because of these limitations, we have defined a new type of security pattern called
Enterprise Security Pattern. This new type of pattern tries to improve the usability of
security patterns by incorporating them in a more comprehensive pattern that can
handle more threats. In this paper, we document a new enterprise security pattern that
organizations could apply to protect their information assets when using SaaS.
Companies which have already hired SaaS could also consult this pattern, in order to
verify if they are correctly protecting their assets.
The remainder of this paper is organized as follows. Section 2 provides a brief
description of enterprise security patterns, including their assets, context and solutions
models. Section 3 documents a new enterprise security pattern called Secure Software
as a Service (SaaS). Finally, Section 4 presents some conclusions and future work.
2 Enterprise Security Patterns
An enterprise security pattern is described by four models describing generic enterprise
security architectures that provide some security properties for a set of information
assets in a specific context. These patterns combine in one cohesive pattern: (i) the
information assets to be protected, including their sensitivity level, (ii) the context in
which these assets are found, (iii) the threats associated with the assets, (iv) the security
policies, patterns, mechanisms and technologies used to stop these threats, and (v) the
stakeholders and systems involved in the solution. Here, we show the assets, context
and solution models used by these patterns.
2.1 Assets and Context Model
When building secure systems, organizations should use an information assets
classification, in order to facilitate the security designer’s work. The information assets
should be classified in groups, according to their sensitivity levels, which depend on
the relative value of the asset for the organization. This value may depend on several
aspects or factors. For this reason, when classifying assets, the organizations should
seek support from a risk analysis methodology.
The organizations’ information assets may be classified into three large groups:
15