Copy on write technique to modify a shared memory page has been a novel idea by keeping the original page unchanged and modifying a duplicate copy of it. The modifiable content in a page can range from one byte to a complete page. The process which owns the page to be modified is kept suspended until the whole page is copied down. Page copying is done without caring the size of modifiable content. Process suspension and page content copying take further time. Also minor page fault is raised as further activity. COW technique, in virtual machines, to save redundant physical memory space is resulting today in memory disclosure attacks. Our work BMCOW as bytes modification & COW modifies shared pages in a way such that COW works on only unreferenced bytes of the pages and thus it avoids extra time of modification process. This avoids any known timing based attacks on virtual machines' memory. © 2015 IEEE.