This stands for Secure Hash Algorithm, and it was developed by the National Security Agency. You will notice, as with all information presented in hex, that the numbers 0–9 and the letters a–f are used. This value is displayed as 32 hexadecimal characters. This hash algorithm produces a unique 128-bit value of data. MD5 was developed by Ron Rivest, who is a professor at the Massachusetts Institute of Technology. As the name suggests, this algorithm is in its fifth reincarnation. MD5 is an acronym for Message Digest Algorithm 5. We will focus primarily on two different hash types: MD5 and SHA1. A hash value is often referred to as a file's DNA or digital fingerprint. It is possible to create a forensic hash of a file, of a series of files, or of an entire hard drive. Hashing is the application of a mathematical formula to uniquely identify the contents of a specific file. In the digital forensic and e-discovery field, hashing is most commonly used as a means for file identification. Hashing has evolved into a widely used function with numerous applications in the computer industry, including databases, passwords, encryptions, and many others. In E-discovery: Creating and Managing an Enterprisewide Program, 2009 Hashing Unlike Windows executables, which are identifiable by their distinct MZ file signature, forever cementing the initials of one of the MS-DOS architects into the file format, the ELF files signature is “ELF” or the hexadecimal characters 7f 45 4c 46. Although there is a broad scope of malicious code and exploits that can attack and compromise a Linux system, ranging from shell scripts to java scripts and other formats, most Linux-based malware specimens are executable files.
For example, a Portable Network Graphics file (.png extension) begins with the hexadecimal characters 89 50 4e 47, which translates to the letters “.PNG” in the first 4 bytes of the file.
Different file types have different file signatures. On a Linux system, a file signature is normally contained within the first few bytes of the file. A file signature is a unique sequence of identifying bytes written to a file's header. Aquilina, in Malware Forensics, 2008 File Typesīecause we cannot rely upon a file's extension as a sole indicator of its contents or its file type, we need to examine a file's signature.
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