TCP Congestion Control Flag (ECN) Probe
Attack Pattern ID: 325 (Detailed Attack Pattern)Typical Severity: LowStatus: Draft
+ Description

Summary

This OS fingerprinting probe checks to see if the remote host supports explicit congestion notification (ECN) messaging. ECN messaging was designed to allow routers to notify a remote host when signal congestion problems are occurring. Explicit Congestion Notification messaging is defined by RFC 3168. Different operating systems and versions may or may not implement ECN notifications, or may respond uniquely to particular ECN flag types.

+ Target Attack Surface

Target Attack Surface Description

Targeted OSI Layers: Network Layer

Target Attack Surface Localities

Server-side

Target Attack Surface Types: Host

Target Functional Services

Target Functional Service 1: None
Protocol 1: IPProtocol 2: TCP
Protocol Header 1: IP Header
Protocol RFCProtocol Field NameProtocol Field DescriptionProtocol Operation Code
RFC 3168
Explicit Congestion Notification (ECN) field. Bits 6 and 7 in the IPv4 TOS octet are designated as the ECN field.
The not-ECT codepoint '00' indicates a packet that is not using ECN.
00
Protocol Header 2: IP Header
Protocol RFCProtocol Field NameProtocol Field DescriptionProtocol Operation Code
RFC 3168
Explicit Congestion Notification (ECN) field. Bits 6 and 7 in the IPv4 TOS octet are designated as the ECN field.
The ECT(1) bit. Binary flag '01' indicates a packet is using ECN(1) channel.
01
Protocol Header 3: IP Header
Protocol RFCProtocol Field NameProtocol Field DescriptionProtocol Operation Code
RFC 3168
Explicit Congestion Notification (ECN) field. Bits 6 and 7 in the IPv4 TOS octet are designated as the ECN field.
The ECT(0) bit. Binary flag '10' indicates a packet is using ECT(0) channel.
10
Protocol Header 4: IP Header
Protocol RFCProtocol Field NameProtocol Field DescriptionProtocol Operation Code
RFC 3168
Explicit Congestion Notification (ECN) field. Bits 6 and 7 in the IPv4 TOS octet are designated as the ECN field.
The CE codepoint '11' is set by a router to indicate congestion to the end nodes.
11
Related Protocol: Internet Protocol
Relationship Type
Uses Protocol
Protocol Header 5: TCP Header
Protocol RFCProtocol Field NameProtocol Field DescriptionProtocol Operation Code
RFC 3168
Reserved Field
ECN-Echo flag. The ECN-Echo flag is assigned to Bit 9 in the Reserved field of the TCP header.
ECE
Protocol Header 6: TCP Header
Protocol RFCProtocol Field NameProtocol Field DescriptionProtocol Operation Code
RFC 3168
Reserved Field
CWR Flag. The CWR flag is assigned to Bit 8 in the Reserved field of the TCP header.
CWR
Related Protocol: Transmission Control 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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