An internet leak is the unauthorized release of information over the internet. Various types of information and data can be, and have been, "leaked" to the Internet, the most common being personal information, computer software and source code, and artistic works such as books or albums. For example, a musical album is leaked if it has been made available to the public on the Internet before its official release date.
Source code leaks are usually caused by misconfiguration of software like CVS or which allow people to get source files through exploits, software bugs, or employees that have access to the sources or part of them revealing the code in order to harm the company.
There were many cases of source code leaks in the history of software development.
As Fraunhofer IIS released in 1994 only a low quality version of their MP3 encoding software (l3enc), a hacker named SoloH gathered the source code from the unprotected servers of the University of Erlangen and developed a higher quality version, which started the MP3 revolution on the internet.
Around 1996 Electronic Arts accidentally put the source code of the video game FIFA 97 on a demo disc.
In 2003, Axel Gembe, a German hacker, who had infiltrated Valve's internal network months earlier, exploited a security hole in Microsoft's Outlook to get the complete source of the video game Half-Life 2. The source code was leaked online a week later, a playable version of Half-Life 2 was compiled from the source code, revealing how unfinished it was. The leaks damaged morale at Valve and slowed development. In March 2004, Gembe contacted Gabe Newell, CEO of Valve, and identified himself, saying he was a fan and had not acted maliciously. Newell worked with the FBI to invite Gembe to a fake job interview, planning to have him arrested in the USA; however, police arrested him in Germany. The complete source was soon available in various s.
Also in 2003, source code to Diebold Election Systems Inc. voting machines was leaked.