Making some unwanted material difficult to understand, inside some legit material is termed as Obfuscation. This term has been extensively used by Malware Practitioners to make their illegal code very hard to detect ,thus making reverse engineering of their malware ,a difficult task.
It’s full form is Open Source Intelligence. This term is used in reference to the act of collecting data from the open source or publicly available for intelligence purpose. Many OSINT tools are available which plays an important role to gather information for forensic use.