: Protecting Data Warehouse (DW) is very important, since it consists of sensitive data used in many business models for decision support processes. Data masking and encryption techniques have been recommended in academic literatures for DW, however, most of the previous works considered only the numeric data types. This research proposes an improved Modulus Based Technique (MOBAT) that supports string data with numeric and non-numeric attributes. Java with NetBeans and MySQL were used in developing the solution. The experimental results show that our suggested technique achieves low storage space overhead, loading time overhead and better processing time performance as compared to the existing system. While existing system consumed 102MB storage space after MOBAT was applied to the data (8% storage space overhead), the proposed methodology maintained the same storage space (1172mb) when data was without encryption and when MOBAT was applied. This means that no extra space is added. Also, loading time overhead for existing system was 7%, but the new scheme achieved 6%. Based on the experimental results obtained, our technique is more efficient, making it a valid alternative for protecting data stored in DWs.