Introduction to Cyber Security

STEGANOGRAPHY

It is a technique of hiding secret messages in a document file, image file, and program or protocol etc. such that the embedded message is invisible and can be retrieved using special software. Only the sender and the receiver know about the existence of the secret message in the image. The advantage of this technique is that these files are not easily suspected.



Figure 8: Steganography⁶
There are many applications of steganography which includes sending secret messages without ringing the alarms, preventing secret files from unauthorized and accidental access and theft , digital watermarks for IPR issues, etc.

Let us discuss how the data is secretly embeded inside the cover file( the medium like image, video, audio, etc which is used for embed secret data) without being noticed. Let us take an example of an image file which is used as a cover mediem. Each pixel of a high resolution image is represented by 3 bytes(24 bits). If the 3 least significant bits of this 24 bits are altered and used for hiding the data, the resultant image, after embeded the data into it, will have un- noticible change in the image quality and only a very experienced and tranined eyes can detect this change. In this way, evcery pixel can be used to hide 3 bits of information.

Similerly, introducing a white noise in an audio file at regular or randon interval can be used to hide data in an audio or video files. There are various free softwares available for Steganography. Some of the popular ones are: QuickStego, Xiao, Tucows, OpenStego, etc.
⁶ Image courtesy: https://upload.wikimedia.org/wikipedia/commons/b/b8/Seformatbmp-embedding_full.png

INVESTIGATING CYBER CRIMES: INTRODUCTION TO CYBER FORENSIC

In the precedding chapters, we have dicussed the prevention techniques for cyber attack. What if one have encounter cyber attack? What Next? The next step is to report the cyber crime. But if a person is exposed to cyber forensic principles, the chances that the person accidently distroy the vital cyber evidences are minimized.

1.