Techniques for providing data loss prevention, including data exfiltration prevention and crypto-ransomware prevention, are provided. In some embodiments, a slack-space file system is created by using a modified packing algorithm to increase and/or optimize an amount of slack space created by files stored in a standard file system. A program for accessing and indexing the slack-space file system may be stored, and requests by a user to store data on a storage medium of a computer system may cause the information to be stored in the slack-space file system, where it may be protected from destructive malware that operates solely on the standard file system. In some embodiments, sensitive information may be hidden by storing the information in an alternate data stream of a file and by replacing the information in the unnamed data stream of the file with non-sensitive information that may appear to be sensitive.