IMPORTANT: No additional bug fixes or documentation updates
will be released for this version. For the latest information, see the
current release documentation.
Direct Outbound SMB Connection
editDirect Outbound SMB Connection
editIdentifies unexpected processes making network connections over port 445. Windows File Sharing is typically implemented over Server Message Block (SMB), which communicates between hosts using port 445. When legitimate, these network connections are established by the kernel. Processes making 445/tcp connections may be port scanners, exploits, or suspicious user-level processes moving laterally.
Rule type: eql
Rule indices:
- winlogbeat-*
- logs-endpoint.events.*
- logs-windows.*
Severity: medium
Risk score: 47
Runs every: 5m
Searches indices from: now-9m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
References: None
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Lateral Movement
Version: 9
Rule authors:
- Elastic
Rule license: Elastic License v2
Investigation guide
edit## Triage and analysis ### Investigating Direct Outbound SMB Connection This rule looks for unexpected processes making network connections over port 445. Windows file sharing is typically implemented over Server Message Block (SMB), which communicates between hosts using port 445. When legitimate, these network connections are established by the kernel (PID 4). Occurrences of non-system processes using this port can indicate port scanners, exploits, and tools used to move laterally on the environment. #### Possible investigation steps - Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures. - Investigate other alerts associated with the user/host during the past 48 hours. - Contact the account owner and confirm whether they are aware of this activity. - Investigate abnormal behaviors observed by the subject process such as network connections, registry or file modifications, and any spawned child processes. - Retrieve the process executable and determine if it is malicious: - Use a private sandboxed malware analysis system to perform analysis. - Observe and collect information about the following activities: - Attempts to contact external domains and addresses. - File and registry access, modification, and creation activities. - Service creation and launch activities. - Scheduled tasks creation. - Use the PowerShell Get-FileHash cmdlet to get the files' SHA-256 hash values. - Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc. ### False positive analysis - If this rule is noisy in your environment due to expected activity, consider adding exceptions — preferably with a combination of user and command line conditions. ### Response and remediation - Initiate the incident response process based on the outcome of the triage. - Isolate the involved host to prevent further post-compromise behavior. - If the triage identified malware, search the environment for additional compromised hosts. - Implement temporary network rules, procedures, and segmentation to contain the malware. - Stop suspicious processes. - Immediately block the identified indicators of compromise (IoCs). - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system. - Remove and block malicious artifacts identified during triage. - Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components. - Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector. - Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
Rule query
editsequence by process.entity_id [process where event.type == "start" and process.pid != 4] [network where destination.port == 445 and process.pid != 4 and not cidrmatch(destination.ip, "127.0.0.1", "::1")]
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Lateral Movement
- ID: TA0008
- Reference URL: https://attack.mitre.org/tactics/TA0008/
-
Technique:
- Name: Remote Services
- ID: T1021
- Reference URL: https://attack.mitre.org/techniques/T1021/
-
Sub-technique:
- Name: SMB/Windows Admin Shares
- ID: T1021.002
- Reference URL: https://attack.mitre.org/techniques/T1021/002/