Detect Network Topology in CrowdStrike LogScale
Adversaries may gather information about the victim's network topology that can be used during targeting. This includes physical and logical arrangement of external-facing and internal network environments, network devices such as gateways and routers, and routing infrastructure. Threat actors like Volt Typhoon and Salt Typhoon have conducted extensive network topology reconnaissance to identify critical infrastructure paths, upstream/downstream network segments, and inter-network connectivity before executing intrusion campaigns. Detection focuses on two surfaces: (1) network discovery tool execution on managed endpoints indicating an insider or post-compromise enumeration phase, and (2) external scanning patterns visible in perimeter logs indicating pre-compromise reconnaissance by external actors.
MITRE ATT&CK
- Tactic
- Reconnaissance
- Technique
- T1590 Gather Victim Network Information
- Sub-technique
- T1590.004 Network Topology
- Canonical reference
- https://attack.mitre.org/techniques/T1590/004/
LogScale Detection Query
// Branch 1: Network discovery tool process execution
#event_simpleName=ProcessRollup2
| FileName = /(?i)^(nmap|masscan|zmap|netdiscover|nbtscan|arp-scan|unicornscan|lansweeper)(|\.exe)$/
OR CommandLine = /(?i)(nmap|masscan|zmap|tracert|traceroute|pathping|tracepath|snmpwalk|snmpget|snmpenum|get-netroute|get-netneighbor|route\s+print|netstat\s+-r|ip\s+route|arp\s+-[an]|show cdp|show lldp|nmap\s+--traceroute|nmap\s+-O|nmap\s+-sn|arp-scan|netdiscover)/
| eval risk_indicator =
case(
CommandLine = /(?i)(snmpwalk|snmpget|snmpenum|snmpbulk)/, "SNMP_Enumeration",
CommandLine = /(?i)(nmap\s+-[Oo]|os-detection|os-fingerprint)/, "OS_Fingerprinting",
CommandLine = /(?i)(tracert|traceroute|pathping|tracepath)/, "Route_Tracing",
CommandLine = /(?i)(nmap.*-sn|netdiscover|arp\s+-a|arp-scan)/, "Host_Discovery",
CommandLine = /(?i)(get-netroute|route.*print|ip\s+route|netstat.*-r)/, "Routing_Table_Enum",
true, "General_Network_Discovery"
)
| table
[@timestamp, ComputerName, UserName, FileName, CommandLine,
ParentBaseFileName, ParentCommandLine, risk_indicator]
| sort @timestamp desc
// Branch 2: Multi-host scanning on network management protocol ports
// Run as separate query:
// #event_simpleName=NetworkConnectIP4
// | RemotePort in [161, 162, 179, 520, 521, 646, 2049, 8291]
// | groupBy(
// [ComputerName, UserName, ImageFileName, CommandLine],
// function=[
// count(RemoteIP, distinct=true, as=UniqueHosts),
// collect(RemotePort, as=ScannedPorts),
// min(@timestamp, as=FirstSeen),
// max(@timestamp, as=LastSeen)
// ]
// )
// | UniqueHosts > 5
// | eval risk_category = "Broadcast_Protocol_Scanning"
// | table [FirstSeen, ComputerName, UserName, ImageFileName, CommandLine, UniqueHosts, ScannedPorts, risk_category]Detects network topology reconnaissance in CrowdStrike Falcon via two LogScale CQL branches. Branch 1 queries ProcessRollup2 events for execution of network discovery tool binaries or command lines matching topology enumeration patterns, with case-based risk indicator classification. Branch 2 (commented, run separately) correlates NetworkConnectIP4 events to identify hosts making connections to SNMP/BGP/RIP/routing management ports across more than 5 unique remote IPs, indicating active network topology mapping.
Data Sources
Required Tables
False Positives & Tuning
- CrowdStrike Spotlight or Exposure Management scanning modules generating network connection events that resemble multi-host port scanning
- IT administrators using built-in Windows commands (tracert, route print, arp -a) for routine network diagnostics — especially from helpdesk or NOC workstations
- Authorized third-party network discovery agents (Lansweeper, Nmap-based CMDB tools) installed on managed servers running scheduled inventory scans
- Red team or authorized penetration testing engagements using Falcon-monitored endpoints as pivot points during assessed campaigns
Other platforms for T1590.004
Testing Methodology
Validate this detection against 5 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 1Network Topology Discovery via Traceroute and Route Table Enumeration
Expected signal: Sysmon Event ID 1: Process Create events for route.exe, tracert.exe, arp.exe, netstat.exe with their respective command lines. Sysmon Event ID 11: File Create event for route_output.txt in %TEMP%. Sysmon Event ID 3: Network connections from tracert.exe to 8.8.8.8 and intermediate hops. Security Event ID 4688 (if process auditing enabled) for each spawned process.
- Test 2SNMP Network Device Topology Enumeration
Expected signal: Auditd/Sysmon-for-Linux process execution event for snmpwalk with command line containing OIDs .1.3.6.1.2.1.4.22 (ARP table) and .1.3.6.1.2.1.4.24 (routing table). Network connection event (UDP/161) to target host. File creation event for /tmp/snmp_arp_output.txt. Syslog entries from snmpd if local daemon receives the query.
- Test 3PowerShell Network Neighbor and Route Enumeration
Expected signal: Sysmon Event ID 1: Process Create for powershell.exe with CommandLine containing 'Get-NetRoute', 'Get-NetNeighbor', 'Get-NetIPAddress', 'ConvertTo-Json'. PowerShell ScriptBlock Log Event ID 4104 with full script content. Sysmon Event ID 11: File Create event for network_topology.json in %TEMP%.
- Test 4Nmap Host Discovery and OS Detection Scan
Expected signal: Sysmon Event ID 1: Process Create for nmap.exe with CommandLine containing '-sn', '-O', '--osscan-guess', '-oX'. Multiple Sysmon Event ID 3 network connection events for ICMP and TCP probes across the /24 range. Sysmon Event ID 11: File Create events for nmap_discovery.xml and nmap_osdetect.xml in %TEMP%.
- Test 5BGP and Routing Protocol Reconnaissance via Netstat
Expected signal: Auditd/Sysmon-for-Linux process execution events for netstat, ss, ip with command lines containing routing protocol ports (179 BGP, 520 RIP, 646 LDP). File creation events for /tmp/routing_protocols.txt, /tmp/routing_table_full.txt, /tmp/arp_cache.txt. If Sysmon for Linux installed: Event ID 1 (Process Create) for each command.
References (9)
- https://attack.mitre.org/techniques/T1590/004/
- https://dnsdumpster.com/
- https://www.cisa.gov/news-events/cybersecurity-advisories/aa24-038a
- https://blog.talosintelligence.com/salt-typhoon-analysis/
- https://www.mandiant.com/resources/blog/fin13-a-cybercriminal-threat-actor-focused-on-mexico
- https://nmap.org/book/man-output.html
- https://learn.microsoft.com/en-us/powershell/module/nettcpip/get-netroute
- https://learn.microsoft.com/en-us/azure/sentinel/connect-sysmon
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1590.004/T1590.004.md
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