Book Image

Kali Linux 2 - Assuring Security by Penetration Testing - Third Edition

By : Gerard Johansen, Lee Allen, Tedi Heriyanto, Shakeel Ali
Book Image

Kali Linux 2 - Assuring Security by Penetration Testing - Third Edition

By: Gerard Johansen, Lee Allen, Tedi Heriyanto, Shakeel Ali

Overview of this book

Kali Linux is a comprehensive penetration testing platform with advanced tools to identify, detect, and exploit the vulnerabilities uncovered in the target network environment. With Kali Linux, you can apply appropriate testing methodology with defined business objectives and a scheduled test plan, resulting in a successful penetration testing project engagement. Kali Linux – Assuring Security by Penetration Testing is a fully focused, structured book providing guidance on developing practical penetration testing skills by demonstrating cutting-edge hacker tools and techniques with a coherent, step-by-step approach. This book offers you all of the essential lab preparation and testing procedures that reflect real-world attack scenarios from a business perspective, in today's digital age.
Table of Contents (24 chapters)
Kali Linux 2 – Assuring Security by Penetration Testing Third Edition
Credits
Disclaimer
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Understanding the TCP and UDP message format


The TCP message is called a segment. A TCP segment consists of a header and a data section. The TCP header is often 20 bytes long (without TCP options). It can be described using the following figure:

Here is a brief description of each field:

  • The Source Port and the Destination Port have a length of 16 bits each. The source port is the port on the sending machine that transmits the packet, while the destination port is the port on the target machine that receives the packet.

  • The Sequence Number (32 bits), in a normal transmission, is the sequence number of the first byte of data of this segment.

  • The Acknowledgment Number (32 bits) contains the sequence number from the sender, increased by one.

  • H.Len. (4 bits) is the size of the TCP header in 32-bit words.

  • Rsvd. is reserved for future use. It is a 4-bit field and must be zero.

  • The Control Bits (control flags) contains eight 1-bit flags. In the original specification (RFC 793; the RFC can be downloaded...