Detect Network Sniffing in CrowdStrike LogScale
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/
LogScale Detection Query
// Detection 1: Known packet capture tool process execution
(
#event_simpleName = "ProcessRollup2"
| ImageFileName = /(?i)(tcpdump|tshark|wireshark|windump|dumpcap|rawshark|networkminer|intercepter-ng|sniffpass|pcapdump|ntopng|capinfos|editcap|ssldump)/
OR CommandLine = /(?i)(tcpdump|tshark|wireshark|windump|dumpcap|networkminer|intercepter|sniffpass|scapy\.all|pcap_open|pcap_loop|sock_raw|af_packet|libpcap|impacket)/
| eval DetectionType = "KnownSniffingTool"
| eval CaptureToFile = if(CommandLine = /\-w /, "true", "false")
| eval PromiscuousMode = if(CommandLine = /(?i)(\-i any|promisc|\-\-promiscuous)/, "true", "false")
| eval TargetingCleartext = if(CommandLine = /(?i)(port (21|23|80|110|143|389)|ftp|telnet|ldap|smtp|pop3|imap)/, "true", "false")
| table([@timestamp, ComputerName, UserName, UserSid, FileName, ImageFileName, CommandLine, ParentBaseFileName, DetectionType, CaptureToFile, PromiscuousMode, TargetingCleartext])
)
// Detection 2: WinPcap/Npcap driver or DLL loaded by non-standard process
OR
(
#event_simpleName = "ClassifiedModuleLoad"
| ModuleFileName = /(?i)(wpcap\.dll|npcap\.dll|packet\.dll|npf\.sys|npcap\.sys|winpcap\.sys)/
| ImageFileName != /(?i)(wireshark\.exe|tshark\.exe|dumpcap\.exe|rawshark\.exe|capinfos\.exe|editcap\.exe|mergecap\.exe)/
| eval DetectionType = "PacketCaptureDriverLoad"
| eval CaptureToFile = "false"
| eval TargetingCleartext = "false"
| table([@timestamp, ComputerName, UserName, ImageFileName, ModuleFileName, DetectionType, CaptureToFile, TargetingCleartext])
)
// Detection 3: Scripting languages invoking raw socket or pcap APIs
OR
(
#event_simpleName = "ProcessRollup2"
| ImageFileName = /(?i)(python(\.exe|3)?|perl\.exe|ruby\.exe|pwsh\.exe|powershell\.exe)/
| CommandLine = /(?i)(socket\.AF_PACKET|SOCK_RAW|ETH_P_ALL|pcap_open|pcap_loop|pcap_next|libpcap|scapy|impacket)/
| eval DetectionType = "RawSocketViaScripting"
| eval CaptureToFile = if(CommandLine = /(?i)(\-w |wrpcap|pcap_dump)/, "true", "false")
| eval TargetingCleartext = if(CommandLine = /(?i)(port (21|23|80|110|389))/, "true", "false")
| table([@timestamp, ComputerName, UserName, UserSid, ImageFileName, CommandLine, ParentBaseFileName, DetectionType, CaptureToFile, TargetingCleartext])
)
| sort(field=@timestamp, order=desc)CrowdStrike LogScale (Falcon) query detecting T1040 Network Sniffing using three Falcon telemetry event types: ProcessRollup2 events for known packet capture tool execution and scripting-language raw socket invocations, and ClassifiedModuleLoad events for WinPcap/Npcap driver loading by unauthorized parent processes. Enriches detections with capture-to-file and cleartext protocol targeting indicators derived from command line analysis.
Data Sources
Required Tables
False Positives & Tuning
- Authorized security operations personnel running Wireshark or tshark on endpoints during network forensics or incident response investigations with management approval
- Endpoint security sensors or network monitoring agents (e.g., CrowdStrike Falcon sensor itself) loading WinPcap/Npcap libraries as part of their packet inspection capabilities
- DevOps or automation engineers running Python scripts that use Scapy or Impacket for network protocol testing, fuzzing, or integration tests in non-production 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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