The existing Internet Small Computer System Interface (iSCSI) disk data protection measures cannot guarantee that the data will not be stolen when unexpected user logs into the system legally. By combining algorithm of redirect disk read and write, transparent encryption and decryption of disk, local-no-data iSCSI disk data protection mechanism named iSCSI_SEC (iSCSI disk data SECurity) was proposed. The concept of local-no-data means that the important data in iSCSI disk will only be stored in the server and not be stored in the local storage by user operation or program copy or some other reasons, which can guarantee the confidentiality of important data on the disk. iSCSI_SEC was realized in system kernel by loading a layer of disk filter. The experimental results show that compared with TrueCrypt, although iSCSI_SEC decreased the disk read and write performance, but the decrease is less than that of TrueCrypt. iSCSI_SEC not only can guarantee the confidentiality of data on iSCSI disk, but also has better performance than TrueCrypt under the environment of iSCSI.