Because the browser is not closely built into the operating system, it is more 

difficult to use the browser as an entry point for circumventing operating system 

security. All of the browser software runs in user space and not in kernel space. 

This also means that the browser software can be installed as a non root user.

Apart from the fact that security exploits of the browser do not immediately affect 

the operating system, the bug fixing process for the most commonly used 

browsers is usually very fast, most notably within days (and sometimes hours) 

after discovery of the security problem. This  speed to fix  is a result of the active 

involvement of a large and growing community of open source developers, and 

again because only the application is being patched and tested to provide the fix, 

not the host operating system as well.

Another temporary advantage of open source browsers is their small market 

share relative to Internet Explorer on Microsoft Windows, thus making them 

smaller targets for exploitation. This advantage would diminish in the long run as 

more clients begin using alternative open source browsers.

Messaging client security

A messaging client in this context is defined as an application that is used to 

communicate messages with another user of another computer over a TCP/IP 

network, including the Internet. This includes both e mail applications as well as 

instant messaging applications.

Like browser applications, messaging applications for Linux are open source 

software, and they are stand alone applications that are hosted by the operating 

system. This means that all advantages listed in the section about browser 

security are valid for messaging applications as well. 

The open source messaging client can generally handle more than one 

messaging protocol. This means that a choice of a messaging application for the 

Linux client may still provide some flexibility in the choice of which server side 

messaging application or protocol is being used. The choice of client application 

can actually be influenced by the choice of server side application. Thus security 

considerations can be an influence when designing messaging system services 

in a Linux/OSS based environment.

User fencing/security

User security has been an important part of Unix operating systems from their 

early beginnings. Since Linux, like Unix, is inherently a multi user operating 

system, it is possible to use this core feature to separate different security roles 

on the client. Also the fact that there is only one user with all administrative rights 

(the root user) by default helps in keeping the client secure. 

 Chapter 2. The case for migration 

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