VstuplenieTermin "leak (leaktest, leak test data) over the past couple of years has gained popularity among experts in the field of it security. It can be seen in the news, and comparative tables, but for many of the volume and the appointment of the concepts remain unknown. Why do ordinary computer users should carefully look closely to leak test and their characteristics in their daily computer activity? As the results of tests for leakage data can help you in choosing a reliable product to protect your pc? This article aims to answer these questions and more. By reading you will get all the information necessary for understanding and correct interpretation of the results leak tests. What is the leak? Leak test – is a tool or set of procedures for identifying the ability of security solutions to resist attempts by illegal to send personal information in the network. It shows the readiness of the system block the accidental or intentional data leakage. Leak tests originate from the time of the first personal firewalls (firewalls) in the late 90's. The primary task of firewalls that time was control over network activities of applications and prevent attempts to "call home" ("to send the stolen data") unlawful applications. Recently, leak tests strongly modified and new rooted features such as turning off the firewall protection, the use of new types of cross-program collaboration, the exploitation of vulnerable services – are all those techniques that are used by hackers in his writings, and their can be safely attributed to a separate category of test programs.