Anthropic-Cybersecurity-Skills/skills/detecting-lateral-movement-with-zeek/references/api-reference.md

API Reference: Detecting Lateral Movement with Zeek

CLI Usage

# Analyze current Zeek logs
python agent.py /opt/zeek/logs/current/

# Analyze specific date
python agent.py /opt/zeek/logs/2026-03-18/

# Pipe JSON output for further processing
python agent.py /opt/zeek/logs/current/ 2>/dev/null | python -m json.tool

Zeek Log Files Analyzed

Log File	Fields Used	Detection Purpose
conn.log	ts, id.orig_h, id.resp_h, id.resp_p, service, orig_bytes, resp_bytes	Internal lateral-port connections (SMB 445, RDP 3389, WinRM 5985)
smb_mapping.log	ts, id.orig_h, id.resp_h, path, share_type	Admin share access (C$, ADMIN$, IPC$)
smb_files.log	ts, id.orig_h, id.resp_h, action, path, name, size	Executable file writes to network shares
dce_rpc.log	ts, id.orig_h, id.resp_h, endpoint, operation, named_pipe	Remote service creation (svcctl), scheduled tasks (atsvc)
ntlm.log	ts, id.orig_h, id.resp_h, username, domainname, success	Pass-the-Hash detection, NTLM brute force
kerberos.log	ts, id.orig_h, id.resp_h, request_type, client, service, error_msg	Pass-the-Ticket, Kerberos pre-auth failures

Lateral Movement Ports Tracked

Port	Service	ATT&CK Technique
445	SMB	T1021.002 - SMB/Windows Admin Shares
135	DCE/RPC	T1021.003 - Distributed Component Object Model
139	NetBIOS-SSN	T1021.002 - SMB/Windows Admin Shares
3389	RDP	T1021.001 - Remote Desktop Protocol
5985	WinRM-HTTP	T1021.006 - Windows Remote Management
5986	WinRM-HTTPS	T1021.006 - Windows Remote Management
22	SSH	T1021.004 - SSH

Suspicious DCE/RPC Endpoints

Endpoint	Description	Severity
svcctl	Service Control Manager (PsExec pattern)	CRITICAL
atsvc	AT Scheduler Service (at.exe / schtasks)	CRITICAL
ITaskSchedulerService	Task Scheduler v2 (schtasks)	CRITICAL
winreg	Remote Registry manipulation	HIGH
samr	SAM Remote Protocol (user enumeration)	HIGH
lsarpc	LSA Remote Protocol (policy enumeration)	HIGH
srvsvc	Server Service (share/session enumeration)	HIGH
wkssvc	Workstation Service (user enumeration)	HIGH

Detection Types in Output

Finding Type	Severity	Description
lateral_port_connection	INFO	Internal connection on a lateral-movement-associated port
admin_share_access	HIGH	Access to C$, ADMIN$, or IPC$ administrative share
smb_file_write	MEDIUM/CRITICAL	File write to SMB share (CRITICAL if executable)
suspicious_dce_rpc	HIGH/CRITICAL	DCE/RPC call to remote execution endpoint
multi_source_ntlm_auth	HIGH	Single user NTLM authenticating from 3+ source IPs
ntlm_brute_force	HIGH	5+ failed NTLM auth attempts from same source
multi_source_tgt_request	HIGH	Kerberos TGT requested from 3+ source IPs
kerberos_preauth_failure	MEDIUM	Kerberos pre-authentication failure
psexec_pattern	CRITICAL	Correlated SMB exe write + svcctl service creation

Report Output Schema

{
  "summary": {
    "total_findings": 42,
    "by_severity": {"CRITICAL": 3, "HIGH": 15, "MEDIUM": 24},
    "by_type": {"admin_share_access": 8, "suspicious_dce_rpc": 5}
  },
  "top_connection_pairs": [
    {"pair": "10.0.1.50->10.0.1.100:445", "connections": 287}
  ],
  "top_data_transfer_pairs": [
    {"pair": "10.0.1.50->10.0.1.100:445", "bytes": 104857600, "megabytes": 100.0}
  ],
  "findings": []
}

Zeek CLI Commands

# Install BZAR package for ATT&CK detections
zkg install zeek/mitre-attack/bzar

# Extract SMB admin share access
zeek-cut ts id.orig_h id.resp_h path share_type < smb_mapping.log | grep -iE '(C\$|ADMIN\$)'

# Extract DCE/RPC service creation
zeek-cut ts id.orig_h id.resp_h endpoint operation < dce_rpc.log | grep -i svcctl

# Extract failed NTLM authentications
zeek-cut ts id.orig_h id.resp_h username success < ntlm.log | awk '$5 == "F"'

References

• Zeek Documentation: https://docs.zeek.org/
• BZAR (ATT&CK Zeek Analysis Rules): https://github.com/mitre-attack/bzar
• MITRE ATT&CK Lateral Movement: https://attack.mitre.org/tactics/TA0008/
• Zeek Log Formats: https://docs.zeek.org/en/master/logs/index.html
• Zeek SMB Protocol Analyzer: https://docs.zeek.org/en/master/scripts/base/protocols/smb/