TCP Initial Window Size Probe
Attack Pattern ID: 326 (Detailed Attack Pattern)Typical Severity: LowStatus: Draft
+ Description

Summary

This OS fingerprinting probe checks the initial TCP Window size. TCP stacks limit the range of sequence numbers allowable within a session to maintain the "connected" state within TCP protocol logic. The initial window size specifies a range of acceptable sequence numbers that will qualify as a response to an ACK packet within a session. Various operating systems use different Initial window sizes. The initial window size can be sampled by establishing an ordinary TCP connection.

+ Target Attack Surface

Target Attack Surface Description

Targeted OSI Layers: Transport Layer

Target Attack Surface Localities

Server-side

Target Attack Surface Types: Host

Target Functional Services

Target Functional Service 1: None
Protocol 1: TCP
Protocol Header 1: TCP Header
Protocol Field NameProtocol Field DescriptionProtocol Operation CodeProtocol Data
Window
The 16 bit window indicates an allowed number of octets that the sender may transmit before receiving further permission.
ACK
Protocol Header 2: TCP Header
Protocol Field NameProtocol Field DescriptionProtocol Operation CodeProtocol Data
Acknowledgement Number
If the ACK control bit is set this field contains the value of the next sequence number the sender of the segment is expecting to receive. Once a connection is established this is always sent.
ACK
Related Protocol: Internet Protocol
Relationship Type
Uses Protocol
+ Related Attack Patterns
NatureTypeIDNameDescriptionView(s) this relationship pertains toView\(s\)
ChildOfAttack PatternAttack Pattern315TCP/IP Fingerprinting Probes 
Mechanism of Attack (primary)1000
+ References
Stuart McClure, Joel Scambray and George Kurtz. "Hacking Exposed: Network Security Secrets & Solutions". 6th Edition. McGraw Hill, ISBN: 978-0-07-161374-3. 2009.
Defense Advanced Research Projects Agency (DARPA). "RFC793 - Transmission Control Protocol". 1981. <http://www.faqs.org/rfcs/rfc793.html>.
Gordon "Fyordor" Lyon. "Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning". 3rd "Zero Day" Edition, . Insecure.com LLC, ISBN:978-0-9799587-1-7. 2008.
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