Software security flaws begin and end with Web application security

Sadly, the increase in such flawed applications indicates many developers, or the organizations that they work for, do not fully appreciate the environment in which their applications run or the languages used to create them.

An education issue?
"Easy to learn" scripting languages enable anyone with an eye for graphic design to develop and code powerful Web-based applications. Unfortunately, many developers only bother to learn the eye-catching features of a language and not the security issues that need to be addressed. Also, many of the introductory books on coding fail to discuss security. And, as a result, many of the same vulnerabilities that were problematic for developers several years ago remain a problem today. This is perhaps why cross-site scripting (XSS) is now the most common type of application layer attack, while buffer overflow vulnerabilities, the perennial No. 1, has dropped to fourth place. Two other Web application vulnerabilities, SQL injection and PHP remote file inclusion, take second and third spots.

Mitigating Web application flaws
Fortunately, many risks and remedies overlap. Fixing one problem will more than likely fix another. For example, let's look at some of my best

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Now, implementing these recommendations will also help combat cross-site scripting attacks. One measure developers should adopt particularly to prevent XSS, is to encode input data. Encoding transforms potentially dangerous characters into their display equivalents by using character entity references. For example <script> becomes

The PHP remote file-inclusion vulnerability can also be tackled by checking user input combined with the file_exists() function. This function cannot check remote files, and this allows you to first verify whether an included file exists on your local file system.

As you can see, most vulnerabilities arise when user input is not properly checked. If you are in charge of Web development, ensure that all data is filtered, validated, and encoded before using it in your scripts, data access routines and SQL queries.

About the author:
Michael Cobb, CISSP-ISSAP, is the founder and managing director of Cobweb Applications Ltd., a consultancy that offers IT training and support in data security and analysis. He co-authored the book IIS Security and has written numerous technical articles for leading IT publications. Mike is the guest instructor for SearchSecurity.com's Messaging Security School and, as a SearchSecurity.com site expert, answers user questions on application and platform security.

Rate this Tip To rate tips, you must be a member of SearchSecurity.com. Register now to start rating these tips. Log in if you are already a member. BROWSE BY TAG Web Security Advisor,   Application and Platform Security,   Web Security Tools and Best Practices,   Web Application Security,   Application Attacks (Buffer Overflows, Cross-Site Scripting),   VIEW ALL TAGS Digg This!     StumbleUpon     Del.icio.us    RELATED CONTENT Web Security Advisor DNS rebinding defenses still necessary, thanks to Web 2.0 New defenses for automated SQL injection attacks PCI compliance and Web applications: Code review or firewalls? Worst practices: Bad security incidents to avoid Web scanning and reporting best practices Social networking Web site threats manageable with good enterprise policy Enterprise security in 2008: Building trust into the application development process PCI DSS Section 6: A plan for tackling application security Making the case for Web application vulnerability scanners Preparing for uniform resource identifier (URI) exploits Web Application Security Adobe patches ColdFusion vulnerability blocking website attack nCircle statistics show rising Web application vulnerabilities Twitter bugs, DNSSEC and broswer security Month of Twitter Bugs project to document Twitter flaws Are Web application penetration tests still important? IT pros can detect, prevent website vulnerabilities, thwart attacks PCI compliance requirement 6: Systems and applications Trust eroding as social engineering attacks climb in 2009, says Kaspersky expert US-CERT warns of Gumblar, Martuz drive-by exploits XSS bugs, information leakage top list of website vulnerabilities Application Attacks (Buffer Overflows, Cross-Site Scripting) Adobe ColdFusion websites being compromised PCI management: The case for Web application firewalls Month of Twitter Bugs project to document Twitter flaws Adobe issues first quarterly patch release fixing 13 flaws Balancing security and performance: Protecting layer 7 on the network Adobe issues Reader update fixing zero-day flaw The Pipe Dream of No More Free Bugs Security Squad: Federal cybersecurity defenses Oracle issues 43 updates, fixes serious database flaws Attackers target new Microsoft PowerPoint zero-day flaw Application Attacks (Buffer Overflows, Cross-Site Scripting) Research RELATED GLOSSARY TERMS Terms from Whatis.com − the technology online dictionary anonymous Web surfing  (SearchSecurity.com) buffer overflow  (SearchSecurity.com) cache cramming  (SearchSecurity.com) cookie poisoning  (SearchSecurity.com) dictionary attack  (SearchSecurity.com) distributed denial-of-service attack  (SearchSecurity.com) JavaScript hijacking  (SearchSecurity.com) National Computer Security Center  (SearchSecurity.com) threat modeling  (SearchSecurity.com) trigraph  (SearchSecurity.com) RELATED RESOURCES 2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems Search Bitpipe.com for the latest white papers and business webcasts Whatis.com, the online computer dictionary DISCLAIMER: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.