The document discusses various techniques for detecting tampering in digital images, including passive and active methods. Passive methods analyze underlying pixel statistics and properties to detect inconsistencies introduced during tampering, without requiring embedded watermarks. Specific passive techniques discussed are splicing detection, copy-move detection, and statistical-based detection. The document also briefly covers active techniques like digital watermarking and signatures that require embedded signals but can authenticate images. Overall, the document provides an overview of prominent frameworks for passive image tampering detection and localization.