The importance of security is increasing in a current network system. We have found a big security weakness at the file integration when the people download or upload a file and propose a novel solution how to ensure the security of a file. In particular, hash value can be applied to ensure a file due to a speed and architecture of file transfer. Hash server stores all the hash values which are updated by file provider and client can use these values to entrust file when it downloads. FileShader detects to file changes correctly, and we observed that it did not show big performance degradation. We expect FileShader can be applied current network systems practically, and it can increase a security level of all internet users.