Businesses spend millions on firewalls, intrusion-detection systems, and antivirus applications to try to lock down their networks and E-mail systems, but many may not be focusing enough on securing hackers' most favored point of attack: Web applications.

According to a recent Gartner survey of 131 business-technology executives, only 27% of companies seek outside consulting help when it comes to reviewing Internet or intranet application software code review or testing. And according to the InformationWeek Research 2002 Global Information Security Survey, fielded by PricewaterhouseCoopers, companies may want to reconsider the need to bring in outside help for Web application code review. In the past two years, breaches through applications and misconfigurations have soared: In 2002, 30% of companies reported the hacking of known applications as a source of attack, up from 12% in 2001. Poor access controls nearly tripled year over year as a vector of attack by hackers, from 5% in 2001 to 18% in 2002.

The Open Web Application Security Project, an open-source volunteer project staffed by experts, has compiled a list, published this week, that it says represents the most common mistakes that leave Web apps open to attack from hackers. According to the group, many of these flaws are pervasive throughout the Internet and can be exploited by hackers with little programming skills using readily available software tools.

"It's amazing that companies aren't focusing more on Web applications, considering how many attacks are coming over port 80," says Pete Lindstrom, research director at Spire Security. "Web application developers need to print this list out and it should be coffee-stained and dog-eared in a month."

The top 10 security mistakes Web app developers make, according to the Open Web Application Security Project:

• Unvalidated parameters: Information from Web requests isn't validated before being used by a Web application. Attackers can use these flaws to attack backside components through a Web application.

• Broken access control: Restrictions on what authenticated users are allowed to do aren't properly enforced. Attackers can exploit these flaws to access other users' accounts, view sensitive files, or use unauthorized functions.

• Broken account and session management: Account credentials and session tokens aren't properly protected. Attackers who can compromise passwords, keys, session cookies, or other tokens can defeat authentication restrictions and assume other users' identities.

• Cross-site scripting flaws: The Web application can be used as a mechanism to transport an attack to a user's browser. A successful attack can disclose the user's session token, attack the local machine, or spoof content to fool the user.

• Buffer overflows: Web application components in some languages that don't properly validate input can be crashed and, in some cases, used to take control of a process. These components can include CGI, libraries, drivers, and Web application server components.

• Command injection flaws: Web applications pass parameters when they access external systems or the local operating system. If an attacker can embed malicious commands in these parameters, the external system may execute those commands on behalf of the Web application.

• Error-handling problems: Error conditions that occur during normal operation aren't handled properly. If an attacker can cause errors that the Web application doesn't handle, he or she can gain detailed system information, deny service, cause security mechanisms to fail, or crash the server.

• Insecure use of cryptography: Web applications frequently use cryptographic functions to protect information and credentials. These functions and the code to integrate them have proven difficult to code properly, frequently resulting in weak protection.

• Remote administration flaws: Many Web applications let administrators access a site using a Web interface. If these administrative functions aren't very carefully protected, an attacker can gain full access to all aspects of a site.

• Web and application server misconfiguration: Having a strong server configuration standard is critical to a secure Web application. These servers have many configuration options that affect security and aren't secure out of the box.

More information, including the full report, is available free at www.owasp.org.