An adversary engages in activity to detect the operating system or firmware version of a remote target by interrogating a device, server, or platform with a probe designed to solicit behavior that will reveal information about the operating systems or firmware in the environment. Operating System detection is possible because implementations of common protocols (Such as IP or TCP) differ in distinct ways. While the implementation differences are not sufficient to 'break' compatibility with the protocol the differences are detectable because the target will respond in unique ways to specific probing activity that breaks the semantic or logical rules of packet construction for a protocol. Different operating systems will have a unique response to the anomalous input, providing the basis to fingerprint the OS behavior. This type of OS fingerprinting can distinguish between operating system types and versions.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.IP ID Sequencing Probe - (317)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 317 (IP ID Sequencing Probe)
This OS fingerprinting probe analyzes the IP 'ID' field sequence number generation algorithm of a remote host. Operating systems generate IP 'ID' numbers differently, allowing an attacker to identify the operating system of the host by examining how is assigns ID numbers when generating response packets. RFC 791 does not specify how ID numbers are chosen or their ranges, so ID sequence generation differs from implementation to implementation. There are two kinds of IP 'ID' sequence number analysis - IP 'ID' Sequencing: analyzing the IP 'ID' sequence generation algorithm for one protocol used by a host and Shared IP 'ID' Sequencing: analyzing the packet ordering via IP 'ID' values spanning multiple protocols, such as between ICMP and TCP.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.IP 'ID' Echoed Byte-Order Probe - (318)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 318 (IP 'ID' Echoed Byte-Order Probe)
This OS fingerprinting probe tests to determine if the remote host echoes back the IP 'ID' value from the probe packet. An attacker sends a UDP datagram with an arbitrary IP 'ID' value to a closed port on the remote host to observe the manner in which this bit is echoed back in the ICMP error message. The identification field (ID) is typically utilized for reassembling a fragmented packet. Some operating systems or router firmware reverse the bit order of the ID field when echoing the IP Header portion of the original datagram within an ICMP error message.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.IP (DF) 'Don't Fragment Bit' Echoing Probe - (319)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 319 (IP (DF) 'Don't Fragment Bit' Echoing Probe)
This OS fingerprinting probe tests to determine if the remote host echoes back the IP 'DF' (Don't Fragment) bit in a response packet. An attacker sends a UDP datagram with the DF bit set to a closed port on the remote host to observe whether the 'DF' bit is set in the response packet. Some operating systems will echo the bit in the ICMP error message while others will zero out the bit in the response packet.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP Timestamp Probe - (320)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 320 (TCP Timestamp Probe)
This OS fingerprinting probe examines the remote server's implementation of TCP timestamps. Not all operating systems implement timestamps within the TCP header, but when timestamps are used then this provides the attacker with a means to guess the operating system of the target. The attacker begins by probing any active TCP service in order to get response which contains a TCP timestamp. Different Operating systems update the timestamp value using different intervals. This type of analysis is most accurate when multiple timestamp responses are received and then analyzed. TCP timestamps can be found in the TCP Options field of the TCP header.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP Sequence Number Probe - (321)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 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.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP (ISN) Greatest Common Divisor Probe - (322)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 322 (TCP (ISN) Greatest Common Divisor Probe)
This OS fingerprinting probe sends a number of TCP SYN packets to an open port of a remote machine. The Initial Sequence Number (ISN) in each of the SYN/ACK response packets is analyzed to determine the smallest number that the target host uses when incrementing sequence numbers. This information can be useful for identifying an operating system because particular operating systems and versions increment sequence numbers using different values. The result of the analysis is then compared against a database of OS behaviors to determine the OS type and/or version.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP (ISN) Counter Rate Probe - (323)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 323 (TCP (ISN) Counter Rate Probe)
This OS detection probe measures the average rate of initial sequence number increments during a period of time. Sequence numbers are incremented using a time-based algorithm and are susceptible to a timing analysis that can determine the number of increments per unit time. The result of this analysis is then compared against a database of operating systems and versions to determine likely operation system matches.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP (ISN) Sequence Predictability Probe - (324)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 324 (TCP (ISN) Sequence Predictability Probe)
This type of operating system probe attempts to determine an estimate for how predictable the sequence number generation algorithm is for a remote host. Statistical techniques, such as standard deviation, can be used to determine how predictable the sequence number generation is for a system. This result can then be compared to a database of operating system behaviors to determine a likely match for operating system and version.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP Congestion Control Flag (ECN) Probe - (325)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 325 (TCP Congestion Control Flag (ECN) Probe)
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.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP Initial Window Size Probe - (326)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 326 (TCP Initial Window Size Probe)
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.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP Options Probe - (327)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 327 (TCP Options Probe)
This OS fingerprinting probe analyzes the type and order of any TCP header options present within a response segment. Most operating systems use unique ordering and different option sets when options are present. RFC 793 does not specify a required order when options are present, so different implementations use unique ways of ordering or structuring TCP options. TCP options can be generated by ordinary TCP traffic.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.TCP 'RST' Flag Checksum Probe - (328)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 328 (TCP 'RST' Flag Checksum Probe)
This OS fingerprinting probe performs a checksum on any ASCII data contained within the data portion or a RST packet. Some operating systems will report a human-readable text message in the payload of a 'RST' (reset) packet when specific types of connection errors occur. RFC 1122 allows text payloads within reset packets but not all operating systems or routers implement this functionality.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.ICMP Error Message Quoting Probe - (329)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 329 (ICMP Error Message Quoting Probe)
An adversary uses a technique to generate an ICMP Error message (Port Unreachable, Destination Unreachable, Redirect, Source Quench, Time Exceeded, Parameter Problem) from a target and then analyze the amount of data returned or "Quoted" from the originating request that generated the ICMP error message.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.ICMP Error Message Echoing Integrity Probe - (330)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 330 (ICMP Error Message Echoing Integrity Probe)
An adversary uses a technique to generate an ICMP Error message (Port Unreachable, Destination Unreachable, Redirect, Source Quench, Time Exceeded, Parameter Problem) from a target and then analyze the integrity of data returned or "Quoted" from the originating request that generated the error message.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.ICMP IP Total Length Field Probe - (331)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 331 (ICMP IP Total Length Field Probe)
An adversary sends a UDP packet to a closed port on the target machine to solicit an IP Header's total length field value within the echoed 'Port Unreachable" error message. This type of behavior is useful for building a signature-base of operating system responses, particularly when error messages contain other types of information that is useful identifying specific operating system responses.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.ICMP IP 'ID' Field Error Message Probe - (332)1000 (Mechanisms of Attack) > 118 (Collect and Analyze Information) > 224 (Fingerprinting) > 312 (Active OS Fingerprinting) > 332 (ICMP IP 'ID' Field Error Message Probe)
An adversary sends a UDP datagram having an assigned value to its internet identification field (ID) to a closed port on a target to observe the manner in which this bit is echoed back in the ICMP error message. This allows the attacker to construct a fingerprint of specific OS behaviors.