PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Identifying the Threats We Face
363
Monitoring Security
After we finish developing our web application and deploy it to production servers for
people to begin using, our job is not complete. Part of security is monitoring the system
as it operates, looking at logs and other files to see how the system is performing and
being used. Only by keeping a close eye on the operation of the system (or by writing
and running tools to do portions of this for us), can we see whether ongoing security
problems exist and find areas where we might need to spend some time developing
more secure solutions.
Security is, unfortunately, an ongoing battle and, in a certain hyperbolic sense, a battle
that can never be won. Constant vigilance, improvements to our system, and rapid reaction
to any problems are the price to be paid for a smoothly operating web application.
Our Basic Approach
To give ourselves the most complete security solution possible for reasonable effort and
time, we will describe a twofold approach to security.The first part will fall along the
lines of what we have discussed thus far: how to plan for securing our application and
designing features into it that will help keep it safe.Were we compulsive labelers, we
might call this a top-down approach.
In contrast, we might call the second part of our security approach a bottom-up
approach. In this phase we look at all the individual components in our application, such
as the database server, the server itself, and the network on which it resides.We ensure
that not only are our interactions with these components safe, but that the installation
and configuration of these components is safe. Many products install with configurations
that leave us open to attack, and we would do well to learn about these holes and plug
them.
Identifying the Threats We Face
In Chapter 15,“E-commerce Security Issues,” we saw a number of security threats to
our e-commerce applications. In this chapter we focus on a few of these and look at
how to change our development practices with them in mind.
Access to or Modification of Sensitive Data
Part of our job as web application designers and programmers is to ensure that any data
the user entrusts to us are safe, as are any data that we are given from other departments.
When we expose parts of this information to users of our web application, it must be in
such a way that they see only the information that they are permitted to see, and they
most certainly cannot see information for other users.
If we are writing a front end for an online stock or mutual funds trading system, people
who can get access to our account tables might be able to find out such information
as users’ taxpayer identification numbers (Social Security Numbers, or SSN, in the USA),