Big data refers different-different type of data, i.e., structured data means Relational Data, Semi-structured data means XML and unstructured data example :-Word, PDF, Text, Audio, Video etc. Here I have describe only one aspect of big data; other attributes are volume, velocity, value, and veracity. Security is technology issues, which seems to be resolvable in the near-term, but represent long term challenges that require research and new paradigms. This technology needs to be more improvement in terms of development because it suffers from different security problems. This paper will discuss about different security problems and define existing solution.