Could you add more context to your question. What kind of data? You could create an md5sum or other type of checksum list of the files you want to protect. This is how packages are protected against alteration by distro repositories.
http://www.linuxjournal.com/article/2304
http://www.linuxsecurity.com/resourc...to/ch4.en.html
Also look into the fam package to automate monitoring files for alteration.
You will also want to run chkrootkit periodically. If a cracker can install
a root kit, programs like ls & md5sum & ps may be altered to conceal changes. The
best way to check if you suspect a compromise is to check the filesystem off line.
You could check the hashes of system files against a list that you backed up to
a CDROM.
