It happened, that very often thoughts about cloud services are associated with the thoughts about hackers and cloud security. Reports on hacked cloud services come out fairly regularly, and only some companies admit this fact. Each company understands that customer’s trust is a key success factor, that is why sometimes providers prefer to remain silent when it comes to the issues of data leakage, theft and other violation of data security in cloud computing. However, from the description of the services on their sites, we can see a lot of slogans about the high level of security in the cloud that makes us believe that cloud storages are safe as well as they are inexpensive and convenient to use. How safe is it to store data in the data centers of service providers and what do we know about cloud security?