Detect Network Sniffing in Sumo Logic CSE
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/
Sumo Detection Query
(_sourceCategory="windows/sysmon" OR _sourceCategory="windows/system" OR _sourceCategory="linux/syslog" OR _sourceCategory="linux/auditd")
// Parse Sysmon fields from XML or structured log
| parse "Image=*\n" as image nodrop
| parse "CommandLine=*\n" as command_line nodrop
| parse "ImageLoaded=*\n" as image_loaded nodrop
| parse "ServiceName=*\n" as service_name nodrop
| parse "User=*\n" as acting_user nodrop
| parse "Computer=*\n" as host nodrop
| parse "EventID=*\n" as event_id nodrop
// Normalize for case-insensitive matching
| toLowerCase(image) as image_lower
| toLowerCase(command_line) as cmd_lower
| toLowerCase(image_loaded) as loaded_lower
// Detection 1: Known sniffing tool process creation
| eval is_sniff_process = if(
image_lower matches /.*?(tcpdump|tshark|wireshark|windump|dumpcap|rawshark|networkminer|intercepter|sniffpass|pcapdump|ssldump).*?/ OR
cmd_lower matches /.*?(tcpdump|tshark|wireshark|windump|dumpcap|networkminer|intercepter|sniffpass|scapy|pcap_open|pcap_loop|sock_raw|af_packet|impacket|libpcap).*?/,
1, 0)
// Detection 2: WinPcap / Npcap driver loaded by non-standard parent
| eval is_pcap_driver_load = if(
loaded_lower matches /.*?(wpcap\.dll|npcap\.dll|packet\.dll|npf\.sys|npcap\.sys|winpcap\.sys).*?/ AND
NOT (image_lower matches /.*?(wireshark\.exe|tshark\.exe|dumpcap\.exe|rawshark\.exe|capinfos\.exe|editcap\.exe|mergecap\.exe).*?/),
1, 0)
// Detection 3: Scripting language with raw socket / pcap API usage
| eval is_raw_socket_script = if(
image_lower matches /.*?(python|perl\.exe|ruby\.exe|pwsh\.exe|powershell\.exe).*?/ AND
cmd_lower matches /.*?(af_packet|sock_raw|eth_p_all|pcap_open|pcap_loop|libpcap|scapy|impacket).*?/,
1, 0)
| where is_sniff_process = 1 OR is_pcap_driver_load = 1 OR is_raw_socket_script = 1
| eval detection_type = if(is_sniff_process = 1, "KnownSniffingTool",
if(is_pcap_driver_load = 1, "PacketCaptureDriverLoad",
if(is_raw_socket_script = 1, "RawSocketViaScripting", "Unknown")))
| eval capture_to_file = if(cmd_lower matches /.*?-w .*?/, 1, 0)
| eval targeting_cleartext = if(cmd_lower matches /.*?(port 21|port 23|port 80|port 110|port 143|port 389|ftp|telnet|ldap|smtp|pop3|imap).*?/, 1, 0)
| fields _messageTime, host, acting_user, image, command_line, image_loaded, event_id, detection_type, capture_to_file, targeting_cleartext
| sort by _messageTime descSumo Logic query detecting network sniffing (T1040) across three detection patterns using Sysmon and system log sources: known packet capture tool execution by process name or command line, WinPcap/Npcap driver loading by unexpected parent processes, and scripting language invocations with raw socket or libpcap API signatures. Enriches each alert with capture-to-file and cleartext-protocol-targeting indicators.
Data Sources
Required Tables
False Positives & Tuning
- Network operations teams running tcpdump or tshark on Linux servers during authorized packet capture for latency analysis or protocol debugging
- Security monitoring tools such as CrowdStrike Falcon or Carbon Black that load npcap.dll or wpcap.dll as part of kernel-level traffic inspection
- Authorized purple team or red team exercises using Impacket tools (e.g., secretsdump.py) against dedicated lab or test environments
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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