Detection of Proxy Infrastructure Setup and Traffic Bridging

Technique Detected:  Proxy | T1090

ID: DET0445
Domains: Enterprise
Analytics: AN1229, AN1230, AN1231, AN1232, AN1233
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

AN1229

Suspicious process spawning (e.g., rundll32, svchost, powershell, or netsh) followed by network connection creation to internal hosts or uncommon external endpoints on high or non-standard ports.

Log Sources
Data Component Name Channel
Network Connection Creation (DC0082) WinEventLog:Sysmon EventCode=3
Process Creation (DC0032) WinEventLog:Sysmon EventCode=1
Network Traffic Flow (DC0078) NSM:Connections Outbound Connection
Mutable Elements
Field Description
ParentProcessName Legitimate system processes that may rarely spawn network-capable child processes (e.g., `rundll32`, `svchost`).
DestinationPort Watch for high-numbered ports or well-known proxy ports like 1080, 8080, 4444.
TimeWindow Capture unusual spikes in outbound connections over a short period.

AN1230

User-space tools (e.g., socat, ncat, iptables, ssh) used in non-standard ways to establish reverse shells, port-forwarding, or inter-host connections. Often chained with uncommon outbound destinations or SSH tunnels.

Log Sources
Data Component Name Channel
Process Creation (DC0032) auditd:SYSCALL execve
Network Traffic Flow (DC0078) NSM:Flow Connection Tracking
Mutable Elements
Field Description
CommandLinePattern Shell piping into tools like `socat`, `ncat`, or `openssl` for tunnel creation.
OutboundPortRange Flag connections made from internal systems to uncommon high ports externally.
ProcessUserContext Capture low-privilege or unexpected users executing system-level network tools.

AN1231

AppleScript, LaunchAgents, or remote login services (ssh, networksetup) establishing proxy tunnels or dynamic port forwards to external IPs or alternate local hosts.

Log Sources
Data Component Name Channel
Process Creation (DC0032) macos:unifiedlog None
Network Traffic Flow (DC0078) NSM:Firewall pf firewall logs
Network Connection Creation (DC0082) NSM:Flow connection attempts
Mutable Elements
Field Description
TargetDomain Identify suspicious domains often associated with CDN-routed or anonymized endpoints (e.g., Cloudflare, Fastly).
AppleScriptUsage Alert when AppleScript or Automator tools are used for network tunneling tasks.
LaunchAgentSource Monitor for LaunchAgents executing proxy tools or dynamic ports.

AN1232

Direct use of nc, socat, or reverse tunnel scripts initiated by abnormal user contexts or unauthorized VIBs initiating connections from hypervisor to external systems.

Log Sources
Data Component Name Channel
Command Execution (DC0064) esxi:shell None
Network Traffic Flow (DC0078) esxi:vmkernel None
Network Connection Creation (DC0082) NSM:Flow conn.log
Mutable Elements
Field Description
CLICommand Custom proxy or port forwarding scripts executed from ESXi shell.
DestinationIP Unusual outbound connections from ESXi host, particularly to internet.
UserContext Root or elevated users initiating unexpected tunnels.

AN1233

Dynamic or static port forwarding rules added to route traffic through an internal host, or configuration changes to proxy firewall rules not aligned with baselined policy.

Log Sources
Data Component Name Channel
Firewall Rule Modification (DC0051) NSM:Firewall Policy Change / Rule Update
Network Traffic Flow (DC0078) NSM:Flow Flow Creation (NetFlow/sFlow)
Command Execution (DC0064) networkdevice:cli Interface commands
Mutable Elements
Field Description
RuleType Focus on new allow/permit rules with dynamic NAT or port forwarders.
ChangeUser Flag any non-admins initiating proxy config changes.
FlowVolumeDelta Detect sharp changes in bi-directional traffic patterns.