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Addressing SaaS Security

– By Padma Krishnan
This paper identifies some of the best practices and design principles followed by Trigent in developing SaaS applications to address inherent security challenges
Security continues to be one of the biggest concerns for a SaaS based offering. In this paper we will examine three areas of possible information leakage which are:
Information leakage mechanisms in these areas are:
SaaS solution providers need to provide an appropriate security solution model that would help their customers feel confident about their data security, and that these are understood and addressed with the best practices available in the market today. Therefore, this paper will describe general design principles that can be used to best migate the data security concerns as applied to SaaS applicaons.

Security Principles

While there seems to be no silver bullet for solving all the security needs of complex enterprise grade SaaS applications, they require a well thought out interplay of both security architecture and security techniques. When Trigent develops enterprise grade applications, we follow a “Defense in Depth” principle. In short, the “Defense in Depth” principle prescribes building multiple complementary defense levels across the key layers of an application, such as: UI, Business and Data base.
In addition, we compliment this architecture with a wide range of best practice security techniques including physical security access, firewalls, appropriate network access, SSL certificates, two factor authentication, OpenID, etc. It is important to employ the best security techniques at appropriate levels. When done carefully and thoughtfully it will be extremely difficult to compromise your sensive data either accidentally or on purpose.
In the following sections we describe design principles used by Trigent in development of SaaS applications.

Data Security and Encryption

Data Segregation

The most important principle in a SaaS application is that of data segregation which ensures that each Tenant’s data is properly segregated and that no tenant is able to access another tenant’s data. This is achieved by developing a filtering layer between the tenant and the data source so that data access via the filtering layer returns only the selected tenant’s data. This is done by enforcing a context based connection to the database, thus ensuring that only authorized data is returned. Such security blocks are implemented at common access points in the database layer and in the business layer ensuring that a tenant’s data is always properly segregated.

Data Encryption

Another necessary initiative is encrypting selected sensitive database fields such as SSN, bank account details etc. This is to prevent users like administrators who have access to the database from viewing this sensitive information. We typically encrypt these fields by using a combination of keys or a key and an external random sequence of bits (called a “salt”) which is used to further obscure the encrypted data. A commonly used scheme calls for one part of the key for decrypting the sensitive field to be programmed into the application itself, thus making it almost impossible for say, a database administrator to compromise the data. This ensures that data can be decrypted only by an authorized user running the very application itself and not by a database user who gets access to the database otherwise.

Database Encryption

Microsoft SQL Server 2008 provides TDE (Transparent Data Encryption) functionality which does encryption of the underlying data files of the database. Therefore if only the data files get compromised, it is not possible for the intruder to restore the database and access sensive data. TDE therefore provides the ability to comply with many laws, regulations and guidelines established in various industries.

Dual Validation on Client Side and Server Side

Applications making use of JavaScript to perform certain validations are vulnerable to security issues as scripts can be injected to change the behavior of the application. While JavaScript is highly preferred for quicker UI responsive times, they do pose a security risk. Such vulnerabilities should be assessed and another validation should be performed on the server side to ensure the correctness of the data.

Obfuscation of Code Assemblies

Obfusctiaon using proven techniques is recommended for development in environments such as Microsoft.Net applications. This is necessary so the code assemblies may not be otherwise be reverse engineered thus providing insight into how the application’s security works. This also has the additional benefit of protecting the SaaS vendor’s IP. An example of such an obfuscator tool is PreEmptive Dotfuscator for the Microsoft.Net platform should be assessed and another validation should be performed on the server side to ensure the correctness of the data.


New security threats evolve, as SaaS model matures. These pracces will also necessarily evolve or change to keep pace with such needs. The above methods are some of the recent pracces we have established for developing SaaS applicaons. It is also important to standardize on many of these pracces using reusable libraries or components to speed up such implementaons and get reliable, repeatable performance.