CAPEC-321: TCP Sequence Number Probe
This OS fingerprinting probe tests the target system's assignment of TCP sequence numbers. One common way to test TCP Sequence Number generation is to send a probe packet to an open port on the target and then compare the how the Sequence Number generated by the target relates to the Acknowledgement Number in the probe packet. Different operating systems assign Sequence Numbers differently, so a fingerprint of the operating system can be obtained by categorizing the relationship between the acknowledgement number and sequence number as follows: 1) the Sequence Number generated by the target is Zero, 2) the Sequence Number generated by the target is the same as the acknowledgement number in the probe, 3) the Sequence Number generated by the target is the acknowledgement number plus one, or 4) the Sequence Number is any other non-zero number.
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Overview
CAPEC-321 (TCP Sequence Number Probe) is a detailed-level attack pattern catalogued by MITRE in the Common Attack Pattern Enumeration and Classification (CAPEC). It describes a recurring method attackers use to exploit software weaknesses.
What the attacker needs
Prerequisites
- The ability to monitor and interact with network communications.Access to at least one host, and the privileges to interface with the network interface card.
Resources required
- A tool capable of sending and receiving packets from a remote system.
Consequences
What a successful CAPEC-321 attack can achieve.
Read Data
Affects: Confidentiality
Bypass Protection Mechanism, Hide Activities
Affects: Confidentiality, Access Control, Authorization
Frequently asked questions
Common questions about CAPEC-321.
- What is CAPEC-321?
- This OS fingerprinting probe tests the target system's assignment of TCP sequence numbers. One common way to test TCP Sequence Number generation is to send a probe packet to an open port on the target and then compare the how the Sequence Number generated by the target relates to the Acknowledgement Number in the probe packet. Different operating systems assign Sequence Numbers differently, so a fingerprint of the operating system can be obtained by categorizing the relationship between the acknowledgement number and sequence number as follows: 1) the Sequence Number generated by the target is Zero, 2) the Sequence Number generated by the target is the same as the acknowledgement number in the probe, 3) the Sequence Number generated by the target is the acknowledgement number plus one, or 4) the Sequence Number is any other non-zero number.
- What weaknesses does CAPEC-321 target?
- CAPEC-321 exploits 1 CWE weakness, including CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor).
- How severe is CAPEC-321?
- MITRE rates CAPEC-321 as Low severity with medium likelihood of attack.
References
Attack-pattern data is sourced from the MITRE CAPEC catalog (v3.9). Weakness associations link to the corresponding CWE entries on RadicalNotion.AI.
Defend against CAPEC-321
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