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The adversary is trying to figure out your ICS environment.

Discovery consists of techniques that adversaries use to survey your ICS environment and gain knowledge about the internal network, control system devices, and how their processes interact. These techniques help adversaries observe the environment and determine next steps for target selection and Lateral Movement. They also allow adversaries to explore what they can control and gain insight on interactions between various control system processes. Discovery techniques are often an act of progression into the environment which enable the adversary to orient themselves before deciding how to act. Adversaries may use Discovery techniques that result in Collection, to help determine how available resources benefit their current objective. A combination of native device communications and functions, and custom tools are often used toward this post-compromise information-gathering objective.

Techniques in this Tactics Category

Below is a list of all the Discovery techniques in ATT&CK for ICS:

NameTacticsTechnical Description
Control Device IdentificationDiscoveryAdversaries may perform control device identification to determine the make and model of a target device. Management software and device APIs may be utilized by the adversary to gain this information. By identifying and obtaining device specifics, the adversary may be able to determine device vulnerabilities. This device information can also be used to understand device functionality and inform the decision to target the environment.
I/O Module DiscoveryDiscoveryAdversaries may use input/output (I/O) module discovery to gather key information about a control system device. An I/O module is a device that allows the control system device to either receive or send signals to other devices. These signals can be analog or digital, and may support a number of different protocols. Devices are often able to use attachable I/O modules to increase the number of inputs and outputs that it can utilize. An adversary with access to a device can use native device functions to enumerate I/O modules that are connected to the device. Information regarding the I/O modules can aid the adversary in understanding related control processes.
Network Connection EnumerationDiscoveryAdversaries may perform network connection enumeration to discover information about device communication patterns. If an adversary can inspect the state of a network connection with tools, such as netstat, in conjunction with System Firmware, then they can determine the role of certain devices on the network 1. The adversary can also use Network Sniffing to watch network traffic for details about the source, destination, protocol, and content.
Network Service ScanningDiscoveryNetwork Service Scanning is the process of discovering services on networked systems. This can be achieved through a technique called port scanning or probing. Port scanning interacts with the TCP/IP ports on a target system to determine whether ports are open, closed, or filtered by a firewall. This does not reveal the service that is running behind the port, but since many common services are run on specific port numbers, the type of service can be assumed. More in-depth testing includes interaction with the actual service to determine the service type and specific version. One of the most-popular tools to use for Network Service Scanning is Nmap.

An adversary may attempt to gain information about a target device and its role on the network via Network Service Scanning techniques, such as port scanning. Network Service Scanning is useful for determining potential vulnerabilities in services on target devices. Network Service Scanning is closely tied to .

Scanning ports can be noisy on a network. In some attacks, adversaries probe for specific ports using custom tools. This was specifically seen in the Triton and PLC-Blaster attacks.
Network SniffingDiscoveryNetwork sniffing is the practice of using a network interface on a computer system to monitor or capture information2 regardless of whether it is the specified destination for the information.

An adversary may attempt to sniff the traffic to gain information about the target. This information can vary in the level of importance. Relatively unimportant information is general communications to and from machines. Relatively important information would be login information. User credentials may be sent over an unencrypted protocol, such as Telnet, that can be captured and obtained through network packet analysis. Network sniffing can be a way to discover information for Control Device Identification.

In addition, ARP and Domain Name Service (DNS) poisoning can be used to capture credentials to websites, proxies, and internal systems by redirecting traffic to an adversary.
Remote System DiscoveryDiscoveryRemote System Discovery is the process of identifying the presence of hosts on a network3, and details about them. This process is common to network administrators validating the presence of machines and services, as well as adversaries mapping out a network for future-attack targets. An adversary may attempt to gain information about the target network via network enumeration techniques such as port scanning. One of the most popular tools for enumeration is Nmap. Remote System Discovery allows adversaries to map out hosts on the network as well as the TCP/IP ports that are open, closed, or filtered. Remote System Discovery tools also aid in by attempting to connect to the service and determine its exact version. The adversary may use this information to pick an exploit for a particular version if a known vulnerability exists.
Serial Connection EnumerationDiscoveryAdversaries may perform serial connection enumeration to gather situational awareness after gaining access to devices in the OT network. Control systems devices often communicate to each other via various types of serial communication mediums. These serial communications are used to facilitate informational communication, as well as commands. Serial Connection Enumeration differs from I/O Module Discovery, as I/O modules are auxiliary systems to the main system, and devices that are connected via serial connection are normally discrete systems. While IT and OT networks may work in tandem, the exact structure of the OT network may not be discernible from the IT network alone. After gaining access to a device on the OT network, an adversary may be able to enumerate the serial connections. From this perspective, the adversary can see the specific physical devices to which the compromised device is connected to. This gives the adversary greater situational awareness and can influence the actions that the adversary can take in an attack.