Detect Network Sniffing in Elastic Security
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 insecure, unencrypted protocols such as FTP, HTTP Basic Auth, Telnet, POP3, IMAP, and LDAP. Network sniffing may also reveal configuration details, such as running services, version numbers, and other network characteristics necessary for subsequent Lateral Movement and Defense Evasion activities. In cloud-based environments, adversaries may use traffic mirroring services (AWS Traffic Mirroring, GCP Packet Mirroring, Azure vTap) to sniff network traffic from virtual machines. On network devices, adversaries may perform network captures using Network Device CLI commands such as 'monitor capture'. Threat actors including Sandworm Team, Kimsuky, APT33, and Salt Typhoon have used this technique with tools such as Intercepter-NG, SniffPass, Impacket, and custom sniffers.
MITRE ATT&CK
- Tactic
- Credential Access Discovery
- Technique
- T1040 Network Sniffing
- Canonical reference
- https://attack.mitre.org/techniques/T1040/
Elastic Detection Query
sequence by host.id with maxspan=5m
[
any where (
(event.category == "process" and event.type == "start" and (
process.name in~ ("tcpdump", "tshark", "wireshark", "windump", "dumpcap", "rawshark", "networkminer", "intercepter-ng", "sniffpass", "pcapdump", "ntopng", "capinfos", "editcap", "ssldump") or
process.args like~ "*tcpdump*" or process.args like~ "*tshark*" or process.args like~ "*wireshark*" or
process.args like~ "*pcap_open*" or process.args like~ "*pcap_loop*" or process.args like~ "*AF_PACKET*" or
process.args like~ "*SOCK_RAW*" or process.args like~ "*scapy*" or process.args like~ "*impacket*"
)) or
(event.category == "library" and event.type == "load" and (
file.name in~ ("wpcap.dll", "npcap.dll", "Packet.dll", "npf.sys", "npcap.sys", "winpcap.sys") and
not process.name in~ ("Wireshark.exe", "tshark.exe", "dumpcap.exe", "rawshark.exe", "capinfos.exe", "editcap.exe", "mergecap.exe")
))
)
] by host.hostname
/* Alternative: script-based raw socket detection */
process where event.type == "start" and
process.name in~ ("python.exe", "python3", "python3.exe", "perl.exe", "ruby.exe", "pwsh.exe", "powershell.exe") and
(
process.args like~ "*socket.AF_PACKET*" or
process.args like~ "*SOCK_RAW*" or
process.args like~ "*ETH_P_ALL*" or
process.args like~ "*pcap_open*" or
process.args like~ "*pcap_loop*" or
process.args like~ "*libpcap*" or
process.args like~ "*scapy*" or
process.args like~ "*impacket*"
)Detects network sniffing activity via T1040 across three patterns: (1) execution of known packet capture tools such as tcpdump, tshark, wireshark, and intercepter-ng; (2) loading of WinPcap/Npcap capture libraries by non-standard parent processes; and (3) scripting language invocations using raw socket or libpcap patterns consistent with custom network capture tooling.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate network engineers or security teams running Wireshark, tcpdump, or tshark during authorized network diagnostics or troubleshooting sessions
- Security products such as EDR sensors, packet brokers, or network performance monitoring tools that load WinPcap/Npcap libraries as part of normal operation
- Python-based automation scripts using Scapy or Impacket for authorized penetration testing engagements or purple team exercises
Other platforms for T1040
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1tcpdump Passive Capture on All Interfaces (Linux/macOS)
Expected signal: Linux auditd: execve syscall record for /usr/sbin/tcpdump with argv '-i any -w /tmp/t1040_capture_test.pcap -G 30 -W 1'. Kernel syslog/dmesg: '<interface>: entered promiscuous mode'. File creation event for /tmp/t1040_capture_test.pcap. Sysmon for Linux (if deployed) Event ID 1: Process Create with Image=/usr/sbin/tcpdump and CommandLine containing '-i any' and '-w'. File creation event (Sysmon Event ID 11) for the .pcap output.
- Test 2tshark Targeted Credential Protocol Capture (Windows)
Expected signal: Sysmon Event ID 1: Process Create with Image=tshark.exe, CommandLine containing '-f "port 21 or port 23 or port 80 or port 389"', '-w', and output file path. Sysmon Event ID 7: wpcap.dll and npcap.dll loaded by tshark.exe (if not previously loaded). Sysmon Event ID 11: File Create for %TEMP%\t1040_cred_capture.pcapng. Windows System Event ID 7045 (if Npcap driver not previously installed and service is being created for first time).
- Test 3Python Scapy Raw Socket Packet Sniffing (Linux)
Expected signal: Linux auditd: execve syscall for python3 with inline script containing 'scapy', 'sniff', 'SOCK_RAW', 'AF_PACKET'. Auditd socket syscall records for raw socket creation (socket(AF_PACKET, SOCK_RAW, ETH_P_ALL)). Sysmon for Linux Event ID 1 (if deployed): Process Create with Image=python3 and CommandLine matching 'scapy.*sniff'. No file creation event since data is held in memory only.
- Test 4WinDump Windows Packet Capture with Output File
Expected signal: Sysmon Event ID 1: Process Create with Image=windump.exe, CommandLine '-i 1 -c 50 -w %TEMP%\t1040_windump_test.pcap'. Sysmon Event ID 7: wpcap.dll and Packet.dll loaded by windump.exe process. Sysmon Event ID 11: File Create for the .pcap output file. Windows System Event ID 7045 for NPF driver service installation if WinPcap was not previously installed (service name 'NPF').
References (12)
- https://attack.mitre.org/techniques/T1040/
- https://docs.aws.amazon.com/vpc/latest/mirroring/traffic-mirroring-how-it-works.html
- https://cloud.google.com/vpc/docs/packet-mirroring
- https://docs.microsoft.com/en-us/azure/virtual-network/virtual-network-tap-overview
- https://rhinosecuritylabs.com/aws/abusing-vpc-traffic-mirroring-in-aws/
- https://posts.specterops.io/through-the-looking-glass-part-1-f539ae308512
- https://www.tcpdump.org/manpages/tcpdump.1.html
- https://www.wireshark.org/docs/man-pages/tshark.html
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1040/T1040.md
- https://www.us-cert.gov/ncas/alerts/TA18-106A
- https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/ios-embedded-packet-capture/116045-productconfig-epc-00.html
- https://www.mandiant.com/resources/fortinet-malware-ecosystem
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