This is the first in a series of three articles on penetration testing for Web applications. The first installment provides the penetration tester with an overview of Web applications - how they work, how they interact with users, and most importantly . . .
This is the first in a series of three articles on penetration testing for Web applications. The first installment provides the penetration tester with an overview of Web applications - how they work, how they interact with users, and most importantly how developers can expose data and systems with poorly written and secured Web application front-ends.

Web applications are becoming more prevalent and increasingly more sophisticated, and as such they are critical to almost all major online businesses. As with most security issues involving client/server communications, Web application vulnerabilities generally stem from improper handling of client requests and/or a lack of input validation checking on the part of the developer.

The very nature of Web applications - their ability to collate, process and disseminate information over the Internet - exposes them in two ways. First and most obviously, they have total exposure by nature of being publicly accessible. This makes security through obscurity impossible and heightens the requirement for hardened code. Second and most critically from a penetration testing perspective, they process data elements from within HTTP requests - a protocol that can employ a myriad of encoding and encapsulation techniques.

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