Likely real threat: multi-hop C2 tunnel
Summary
An operator at 198.51.100.74 is driving a four-hop path into the network: 10.0.4.17 to 10.0.4.62 to 10.0.9.8, then out on tcp/8443. Every step uses tools the hosts already carry, and the hop carrying the volume runs on an appliance that cannot host an endpoint agent.
Observed facts
- 02:14:09WinRM from 10.0.4.17 to 10.0.4.62: the first contact ever seen between these hostsnetwork
- 02:14:31Root ssh port-forward on 10.0.4.62, launched from a directory posing as a systemd tmpdirEDR
- 02:47:52POST from 10.0.9.8 to 198.51.100.74:8443 with TLS verification disablednetwork
- 06:26:411.9 GB relayed across the third hop in 4 h 12 m, over 47 sessionsnetwork
- 06:26:41198.51.100.74 was registered nine days ago and scores 0.91 for alertsthreat intel
Hypothesis
Hands-on-keyboard command-and-control, relayed through the systems' own tools. No single binary is malicious; the sequence is: WMI spawns a staged DLL, the DLL spawns encoded PowerShell, PowerShell opens WinRM to a new peer, and that peer forwards to an appliance nobody is watching. Endpoint AV is clean on both managed hosts, as it would be.
Confidence
- Network evidence91
- Endpoint corroboration68
- Threat intelligence91
Next actions
- Contain 10.0.4.17 and 10.0.4.62 through the EDR
- Segment 10.0.9.8 at the switch: it cannot run an agent
- Preserve /var/tmp/.systemd-private-6f2a91/ before a reboot clears it
- Keep the block on 198.51.100.74:8443 and check who registered it
