Hive is just another folder on your computer's hard drive, and what SpiderOak One and Groups do is back up Hive and other selected folders on your hard drive. Securing the copies of your files that are in transit or held online is SpiderOak's job, but securing your hard drive is your operating system's job.
The way to protect the files on your computer is to (1) use full partition or disk encryption and (2) log out of your computer before leaving it unattended or loaning it to others. Local encryption is most secure when done at the filesystem level through the operating system, which is why we at SpiderOak don't try to bolt it on after the fact. For more information on disk encryption and our recommendations, see Local Encryption of Files.