Hashing is one of the most common processes run in DFIR. This process allows us to summarize file content and assign a representative and repeatable signature that represents the file's content. We generally employ file and content hashes using algorithms such as MD5, SHA1, and SHA256. These hash algorithms are valuable as we can use them for integrity validation since a change to even one byte of a file's content will completely alter the resulting hash value. These hashes are also commonly used to form whitelists to exclude known or irrelevant content, or alert lists that quickly identify known interesting files. In some cases, though, we need to identify near matches—something that our MD5, SHA1, and SHA256 algorithms can't handle on their own.
One of the most common utilities that assists with similarity analysis is ssdeep, developed by...
