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

Security Threats
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Exposure of Confidential Data
Data stored on your computers, or being transmitted to or from your computers, might
be confidential. It might be information that only certain people are intended to see,
such as wholesale price lists. It might be confidential information provided by a customer,
such as his password, contact details, and credit card number.
We hope you are not storing information on your web server that you do not intend
anyone to see. A web server is the wrong place for secret information. If you were storing
your payroll records or your top secret plan for beating racing ferrets on a computer,
you would be wise to use a computer other than your web server.The web server is
inherently a publicly accessible machine and should contain only information that either
needs to be provided to the public or has recently been collected from the public.
To reduce the risk of exposure, you need to limit the methods by which information
can be accessed and limit the people who can access it.This process involves designing
with security in mind, configuring your server and software properly, programming carefully,
testing thoroughly, removing unnecessary services from the web server, and requiring
authentication.
You need to design, configure, code, and test carefully to reduce the risk of a successful
criminal attack and, equally important, to reduce the chance that an error will leave
your information open to accidental exposure.
You also need to remove unnecessary services from your web server to decrease the
number of potential weak points. Each service you are running might have vulnerabilities.
Each one needs to be kept up to date to ensure that known vulnerabilities are not
present.The services that you do not use might be more dangerous. If you never use the
command rcp, for example, why have the service installed? 1 If you tell the installer that
your machine is a network host, the major Linux distributions and Windows will install a
large number of services that you do not need and should remove.
Authentication means asking people to prove their identity.When the system knows
who is making a request, it can decide whether that person is allowed access. A number
of possible methods of authentication can be employed, but only two forms are commonly
used on public websites: passwords and digital signatures.We talk a little more
about both later.
CD Universe offers a good example of the cost both in dollars and reputation of
allowing confidential information to be exposed. In late 1999, a cracker calling himself
Maxus reportedly contacted CD Universe, claiming to have 300,000 credit card numbers
stolen from the company’s site. He wanted a $100,000 (U.S.) ransom from the site to
destroy the numbers.The company refused and found itself in embarrassing coverage on
the front pages of major newspapers as Maxus doled out numbers for others to abuse.
Data is also at risk of exposure while it traverses a network. Although TCP/IP networks
have many fine features that have made them the de facto standard for connecting
1 Even if you do currently use rcp, you should probably remove it and use scp (secure copy)
instead.