detecting-lateral-movement-with-zeek

name	detecting-lateral-movement-with-zeek
description	Detect lateral movement in network traffic using Zeek (formerly Bro) log analysis. Parses conn.log, smb_mapping.log, smb_files.log, dce_rpc.log, kerberos.log, and ntlm.log to identify SMB file transfers, NTLM account spray activity, remote service execution, and anomalous internal connections.
domain	cybersecurity
subdomain	network-security
tags	["zeek","lateral-movement","smb","dce-rpc","ntlm-spray","network-forensics"]
version	1.0
author	mahipal
license	Apache-2.0
nist_csf	["PR.IR-01","DE.CM-01","ID.AM-03","PR.DS-02"]
mitre_attack	["T1046","T1040","T1557","T1071","T1021"]

Detecting Lateral Movement with Zeek

Analyze Zeek network logs to identify lateral movement techniques including SMB admin share access, DCE/RPC remote service creation, NTLM account spray, Kerberos ticket anomalies, and large internal data transfers indicative of staging or exfiltration between hosts.

When to Use

• Hunting for lateral movement after an initial compromise indicator is found on one endpoint
• Investigating suspected NTLM account spray or Pass-the-Ticket attacks across the internal network
• Monitoring SMB traffic for unauthorized file transfers to admin shares (C$, ADMIN$, IPC$)
• Detecting remote service execution via DCE/RPC (PsExec, schtasks, WMI lateral patterns)
• Building alerting rules for internal network anomalies in a Zeek-based NSMP deployment
• Performing post-incident timeline reconstruction using Zeek logs as a network-level evidence source

Do not use as a standalone detection mechanism. Zeek sees network traffic only; combine with endpoint telemetry (Sysmon, EDR) for full visibility. Encrypted SMB3 traffic may limit Zeek's visibility into file-level details.

Prerequisites

• Zeek 6.0+ deployed on a network tap or SPAN port monitoring internal VLAN traffic
• Zeek SMB analyzer enabled (loaded by default: @load base/protocols/smb)
• Zeek DCE/RPC analyzer enabled (@load base/protocols/dce-rpc)
• Zeek Kerberos analyzer enabled (@load base/protocols/krb)
• Python 3.8+ (standard library only)
• Access to Zeek log directory (default: /opt/zeek/logs/current/)
• Familiarity with Zeek TSV log format (fields separated by \t, header lines prefixed with #)

Workflow

Step 1: Verify Zeek Log Collection

Confirm that Zeek is producing the required log files for lateral movement detection:

# Check that all required analyzers are producing logs
ls -la /opt/zeek/logs/current/conn.log
ls -la /opt/zeek/logs/current/smb_mapping.log
ls -la /opt/zeek/logs/current/smb_files.log
ls -la /opt/zeek/logs/current/dce_rpc.log
ls -la /opt/zeek/logs/current/kerberos.log
ls -la /opt/zeek/logs/current/ntlm.log

# Quick field check on conn.log
zeek-cut id.orig_h id.resp_h id.resp_p proto service < /opt/zeek/logs/current/conn.log |  -20