The document reviews various image processing techniques developed for counterfeit currency note authentication, emphasizing the need for automated detection in response to increasing counterfeiting challenges. It discusses algorithms and systems utilizing MATLAB and cloud computing, including feature extraction methods like grid-based analysis and neural networks, achieving an average success rate of 92.30% in detecting fake Indian currency notes. The paper concludes that current systems have limitations that can be addressed by utilizing the MapReduce paradigm for improved efficiency and open access.