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Home > CAPEC List > CAPEC-297: TCP ACK Ping (Version 3.9)  


Attack Pattern ID: 297
Abstraction: Detailed
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+ Description
An adversary sends a TCP segment with the ACK flag set to a remote host for the purpose of determining if the host is alive. This is one of several TCP 'ping' types. The RFC 793 expected behavior for a service is to respond with a RST 'reset' packet to any unsolicited ACK segment that is not part of an existing connection. So by sending an ACK segment to a port, the adversary can identify that the host is alive by looking for a RST packet. Typically, a remote server will respond with a RST regardless of whether a port is open or closed. In this way, TCP ACK pings cannot discover the state of a remote port because the behavior is the same in either case. The firewall will look up the ACK packet in its state-table and discard the segment because it does not correspond to any active connection. A TCP ACK Ping can be used to discover if a host is alive via RST response packets sent from the host.
+ Typical Severity


+ Relationships
Section HelpThis table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
ChildOfStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.292Host Discovery
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Prerequisites
The ability to send an ACK packet to a remote host and identify the response. Creating the ACK packet without building a full connection requires the use of raw sockets. As a result, it is not possible to send a TCP ACK ping from some systems (Windows XP SP 2) without the use of third-party packet drivers like Winpcap. On other systems (BSD, Linux) administrative privileges are required in order to write to the raw socket.
The target must employ a stateless firewall that lacks a rule set that rejects unsolicited ACK packets.
The adversary requires the ability to craft custom TCP ACK segments for use during network reconnaissance. Sending an ACK ping requires the ability to access "raw sockets" in order to create the packets with direct access to the packet header.
+ Resources Required
ACK scanning can be performed via the use of a port scanner or by raw socket manipulation using a scripting or programming language. Packet injection tools are also useful for this purpose. Depending upon the technique used it may also be necessary to sniff the network in order to see the response.
+ Consequences
Section HelpThis table specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Access Control
Bypass Protection Mechanism
Hide Activities
+ Mitigations
Leverage stateful firewalls that allow for the rejection of a packet that is not part of an existing connection.
+ Taxonomy Mappings
Section HelpCAPEC mappings to ATT&CK techniques leverage an inheritance model to streamline and minimize direct CAPEC/ATT&CK mappings. Inheritance of a mapping is indicated by text stating that the parent CAPEC has relevant ATT&CK mappings. Note that the ATT&CK Enterprise Framework does not use an inheritance model as part of the mapping to CAPEC.
Relevant to the ATT&CK taxonomy mapping (see parent )
+ References
[REF-33] Stuart McClure, Joel Scambray and George Kurtz. "Hacking Exposed: Network Security Secrets & Solutions". Chapter 2: Scanning, pg. 49. 6th Edition. McGraw Hill. 2009.
[REF-128] Defense Advanced Research Projects Agency Information Processing Techniques Office and Information Sciences Institute University of Southern California. "RFC793 - Transmission Control Protocol". Defense Advanced Research Projects Agency (DARPA). 1981-09. <>.
[REF-34] Gordon "Fyodor" Lyon. "Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning". Section 3.6.2 TCP ACK Ping, pg. 61. 3rd "Zero Day" Edition,. LLC, ISBN: 978-0-9799587-1-7. 2008.
[REF-125] Mark Wolfgang. "Host Discovery with Nmap". 2002-11. <>.
+ Content History
Submission DateSubmitterOrganization
(Version 2.6)
CAPEC Content TeamThe MITRE Corporation
Modification DateModifierOrganization
(Version 2.12)
CAPEC Content TeamThe MITRE Corporation
Updated Attack_Prerequisites, Description, Description Summary, Related_Weaknesses, Resources_Required, Solutions_and_Mitigations
(Version 3.2)
CAPEC Content TeamThe MITRE Corporation
Updated Related_Attack_Patterns
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Page Last Updated or Reviewed: July 31, 2018