# Main Issues in Big Data Security
## 3 Systematic Mapping Study
### Main Topics Found
#### 3.5.1 Infrastructure Security  
When discussing infrastructure security, it is necessary to highlight the main technologies and frameworks found as regards securing the architecture of a Big Data system, and particularly those based on the Hadoop technology, since it is that most frequently used. In this section we shall also discuss certain other topics, such as communication security in Big Data, or how to achieve high-availability. Figure 3 contains a graphic that shows the main topics found and the quantity of papers dealing with each specific topic. The graphic shows that the main topic dealt with by those researching infrastructure security is security for Hadoop. As explained in previous sections, Hadoop can be considered as a de facto  
Figure 3: Main topics regarding infrastructure security. standard for implementing a Big Data environment in a company. The security problems related to this technology have, therefore, been widely discussed by researchers, who have also proposed various methods with which to improve the security of the Hadoop system. This category is probably the most transverse since, in order to protect it, the solutions use different security mechanisms such as authenticity or cryptography. For example, there is a proposal for a security model for G-Hadoop (an extension of the MapReduce framework to run on multiple clusters) that simplifies users' authentication and some security mechanisms in order to protect the system from traditional attacks [27]. A few papers focus on protecting the data that is stored in the HDFS by proposing a new schema [24], a secure access system [28], or even the creation of an encryption scheme [29]. Availability  
Researchers have also dealt with the subject of availability in Big Data systems. One of the main characteristics of Big Data environments, and by extension of a Hadoop implementation, is the availability attained by the use of hundreds of computers in which the data are not only stored, but are also replicated along the cluster. Finding an architecture that will ensure the full availability of the system is, therefore, a priority. For instance, in [30] the authors propose a solution with which to achieve high availability by having multiple active NameNodes at the same time. Other solutions are based on creating a new infrastructure of the storage system so as to improve availability and fault tolerance [31; 32]. Another different approach is that of describing a new Big Data architecture, or modifying the typical one, in order to improve the security of the environment. The authors of [33] propose a new architecture based on the Hadoop file system which, when combined with network coding and multi-node reading, makes it possible to improve the security of the system. Another solution focuses on secure group communications in large-scale networks managed by Big Data systems, and this is achieved by creating certain protocols and changing the infrastructure of the nodes [34]. Authentication  
The value of the data obtained after executing a Big Data process can, to a great extent, be determined by its authenticity. A few papers deal with this problem by proposing solutions related to authentication. In [35], the authors suggest solving the problem of authentication by creating an identity-based _signcryption_ scheme for Big Data. Communication Security  
The security as regards communications between different parts of the Big Data ecosystem is a topic that often is ignored, and only a small number of papers therefore deal with this problem. One paper approaches the topic by explaining the regular data life cycle in a Big Data system, following the different network protocols and applications that the data pass through. The authors also enumerate the main data transfer security techniques [36]. Summary  
With regard to the topic of infrastructure security, the main problem dealt with by researchers would appear to be security for Hadoop systems.