T1040: Network Sniffing
Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network. Network sniffing refers to using the network interface on a system to monitor or capture information sent over a wired or wireless connection. An adversary may place a network interface into promiscuous mode to passively access data in transit over the network, or use span ports to capture a larger amount of data.
Data captured via this technique may include user credentials, especially those sent over an insecure, unencrypted protocol. Techniques for name service resolution poisoning, such as Name Resolution Poisoning and SMB Relay, can also be used to capture credentials to websites, proxies, and internal systems by redirecting traffic to an adversary.
Network sniffing may reveal configuration details, such as running services, version numbers, and other network characteristics (e.g. IP addresses, hostnames, VLAN IDs) necessary for subsequent Lateral Movement and/or Stealth activities. Adversaries may likely also utilize network sniffing during Adversary-in-the-Middle (AiTM) to passively gain additional knowledge about the environment.
In cloud-based environments, adversaries may still be able to use traffic mirroring services to sniff network traffic from virtual machines. For example, AWS Traffic Mirroring, GCP Packet Mirroring, and Azure vTap allow users to define specified instances to collect traffic from and specified targets to send collected traffic to. Often, much of this traffic will be in cleartext due to the use of TLS termination at the load balancer level to reduce the strain of encrypting and decrypting traffic. The adversary can then use exfiltration techniques such as Transfer Data to Cloud Account in order to access the sniffed traffic.
On network devices, adversaries may perform network captures using Network Device CLI commands such as `monitor capture`.
How it's found
Detection Strategy for Network Sniffing Across Platforms: Detects suspicious execution of network monitoring tools (e.g., Wireshark, tshark, Microsoft Message Analyzer), driver loading indicative of promiscuous mode, or non-admin user privilege escalation to access NICs for capture. Correlates interface mode changes to promiscuous with execution of sniffing tools like tcpdump, tshark, or custom pcap libraries. Detects abnormal NIC configurations and unauthorized sniffing from non-root sessions. Detects enabling of interface sniffing via packet capture tools or AppleScript triggering `tcpdump`. Leverages Unified Logs and process lineage to identify suspicious use of `pfctl`, `tcpdump`, or `libpcap` libraries. Detects creation of traffic mirroring sessions (e.g., AWS VPC Traffic Mirroring, Azure vTAP) that redirect traffic from critical assets to other virtual instances, often followed by file creation or session establishment. Detects execution of capture commands via CLI (`monitor capture`, `debug packet`, etc.) or unauthorized CLI access followed by logging configuration changes on Cisco/Juniper/Arista gear.
Standards mapping
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is T1040 Network Sniffing?
Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network. Network sniffing refers to using the network interface on a system to monitor or capture information sent over a wired or wireless connection. An adversary may place a network interface into promiscuous mode to passively access data in transit over the network, or use span ports to capture a larger amount of data. Data captured via this technique may include user credentials, especially those sent over an insecure, unencrypted protocol. Techniques for name service resolution poisoning, such as Name Resolution Poisoning and SMB Relay, can also be used to capture credentials to websites, proxies, and internal systems by redirecting traffic to an adversary. Network sniffing may reveal configuration details, such as running services, version numbers, and other network characteristics (e.g. IP addresses, hostnames, VLAN IDs) necessary for subsequent Lateral Movement and/or Stealth activities. Adversaries may likely also utilize network sniffing during Adversary-in-the-Middle (AiTM) to passively gain additional knowledge about the environment. In cloud-based environments, adversaries may still be able to use traffic mirroring services to sniff network traffic from virtual machines. For example, AWS Traffic Mirroring, GCP Packet Mirroring, and Azure vTap allow users to define specified instances to collect traffic from and specified targets to send collected traffic to. Often, much of this traffic will be in cleartext due to the use of TLS termination at the load balancer level to reduce the strain of encrypting and decrypting traffic. The adversary can then use exfiltration techniques such as Transfer Data to Cloud Account in order to access the sniffed traffic. On network devices, adversaries may perform network captures using Network Device CLI commands such as `monitor capture`.
Which tactics does T1040 belong to?
T1040 maps to the Credential Access, Discovery tactics.
Does TurboPentest test for Network Sniffing?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Related MITRE ATT&CK techniques
About this reference
These security references are maintained by IntegSec, an offensive-security firm whose team holds CISSP, OSCP, and OSCE certifications and has run thousands of penetration tests. Content is kept current as tools, standards, and attack techniques evolve.
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