Vendors should be held more  responsible for buggy software. That's the view of a loose consortium of security experts from more than 30 organisations who have called on enterprises to exert more pressure on their software vendors to ensure that they use secure code development practices.

The group, led by the SANS Institute and Mitre is expected to release draft language for use in procurement contracts between user organisations and software development firms.

The document provides user companies with a list of specific terms and conditions that should be included in procurement contracts to ensure that vendors are adhering to a strict set of software development security standards. In sum, the draft contract would leave development firms liable for software defects.

"Nearly every attack is enabled by [programming] mistakes that provide a handhold for attackers," said Alan Paller, director of research at SANS, a security training and certification group. "The only way programming errors can be eradicated is by making software development organisations legally liable for the errors." he said.

SANS and Mitre are also releasing its second annual CWE/SANS Top 25 list of the most common programming errors currently being made by software developers. The authors say the errors on the list are responsible nearly every major type of cyber attack, including the recent intrusions at Google, and numerous utilities and government agencies.

The list was complied with help from security analysts at numerous organisations including the National Security Agency, the US Department of Homeland Security's National Cyber Security Division, Purdue University, EMC, Symantec and Microsoft.

The Top 25 programming errors found this year are virtually the same as those on the 2009 Top 25 list .

According to the latest list, the most common programming errors continue to be SQL injection errors, cross-site scripting flaws and buffer overflow vulnerabilities All three issues have been well understood for a long time now and have consistently been identified as the most common coding errors on various lists.

Other top vulnerabilities included in this year's list include cross site request forgery flaws, weak access control and authentication mechanisms, overly permissive default settings and a lack of encryption support.

The Top 25 list comes out just days after Trustwave, a provider of security auditing services for major companies, released a report showing that most security breaches continue to be caused by well-known flaws rather than new ones.

Trustwave's report was based on an analysis of data gathered from more than 1,900 penetration tests and over 200 data breach investigations conducted on behalf of clients such as credit card firms American Express, MasterCard, Discover and Visa and several retailers. The Trustwave study found that the top three paths used hackers to gain access to corporate networks in 2009 were via remote access applications, trusted internal network connections and SQL injection attacks -- all well studied issues.

The notion of holding third-party software developers liable for such errors is not new.

Generally it is a good idea to ensure that procurement contracts include language spelling out the security expectations for a project, said Gary McGraw, chief technology officer at Cigital, a security consulting firm. But rather than tying the procurement language to a generalised list of top programming errors, such as the one released today, companies should customise it to their particular environments, he said.

Companies should compile a list of the most common vulnerabilities in their own environments and use that as a basis for the language in their procurement contracts he said. "The notion of controlling your vendors to make sure they are following software security is a very good notion. But it need to tailored to your environment," he said.