Direct Outbound SMB Connection

  1[metadata]
  2creation_date = "2020/02/18"
  3integration = ["endpoint"]
  4maturity = "production"
  5updated_date = "2024/05/21"
  6
  7[transform]
  8[[transform.osquery]]
  9label = "Osquery - Retrieve DNS Cache"
 10query = "SELECT * FROM dns_cache"
 11
 12[[transform.osquery]]
 13label = "Osquery - Retrieve All Services"
 14query = "SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services"
 15
 16[[transform.osquery]]
 17label = "Osquery - Retrieve Services Running on User Accounts"
 18query = """
 19SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services WHERE
 20NOT (user_account LIKE '%LocalSystem' OR user_account LIKE '%LocalService' OR user_account LIKE '%NetworkService' OR
 21user_account == null)
 22"""
 23
 24[[transform.osquery]]
 25label = "Osquery - Retrieve Service Unsigned Executables with Virustotal Link"
 26query = """
 27SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, name, description, start_type, status, pid,
 28services.path FROM services JOIN authenticode ON services.path = authenticode.path OR services.module_path =
 29authenticode.path JOIN hash ON services.path = hash.path WHERE authenticode.result != 'trusted'
 30"""
 31
 32
 33[rule]
 34author = ["Elastic"]
 35description = """
 36Identifies unexpected processes making network connections over port 445. Windows File Sharing is typically implemented
 37over Server Message Block (SMB), which communicates between hosts using port 445. When legitimate, these network
 38connections are established by the kernel. Processes making 445/tcp connections may be port scanners, exploits, or
 39suspicious user-level processes moving laterally.
 40"""
 41from = "now-9m"
 42index = ["logs-endpoint.events.process-*", "logs-endpoint.events.network-*"]
 43language = "eql"
 44license = "Elastic License v2"
 45name = "Direct Outbound SMB Connection"
 46note = """## Triage and analysis
 47
 48### Investigating Direct Outbound SMB Connection
 49
 50This 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.
 51
 52> **Note**:
 53> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/master/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 54
 55#### Possible investigation steps
 56
 57- 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.
 58- Investigate other alerts associated with the user/host during the past 48 hours.
 59- Contact the account owner and confirm whether they are aware of this activity.
 60- Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications, and any spawned child processes.
 61- Examine the host for derived artifacts that indicate suspicious activities:
 62  - Analyze the process executable using a private sandboxed analysis system.
 63  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
 64    - Attempts to contact external domains and addresses.
 65      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
 66      - Examine the DNS cache for suspicious or anomalous entries.
 67        - $osquery_0
 68    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
 69    - Examine the host services for suspicious or anomalous entries.
 70      - $osquery_1
 71      - $osquery_2
 72      - $osquery_3
 73  - Retrieve the files' SHA-256 hash values using the PowerShell `Get-FileHash` cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
 74- Investigate potentially compromised accounts. Analysts can do this by searching for login events (for example, 4624) to the target host after the registry modification.
 75
 76
 77### False positive analysis
 78
 79- 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.
 80
 81### Response and remediation
 82
 83- Initiate the incident response process based on the outcome of the triage.
 84- Isolate the involved host to prevent further post-compromise behavior.
 85- If the triage identified malware, search the environment for additional compromised hosts.
 86  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 87  - Stop suspicious processes.
 88  - Immediately block the identified indicators of compromise (IoCs).
 89  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
 90- Remove and block malicious artifacts identified during triage.
 91- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 92- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 93- 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).
 94"""
 95risk_score = 47
 96rule_id = "c82c7d8f-fb9e-4874-a4bd-fd9e3f9becf1"
 97severity = "medium"
 98tags = [
 99    "Domain: Endpoint",
100    "OS: Windows",
101    "Use Case: Threat Detection",
102    "Tactic: Lateral Movement",
103    "Resources: Investigation Guide",
104    "Data Source: Elastic Defend",
105]
106type = "eql"
107
108query = '''
109sequence by process.entity_id with maxspan=2m
110  [process where host.os.type == "windows" and event.type == "start" and process.pid != 4 and 
111   not user.id : ("S-1-5-19", "S-1-5-20") and 
112   not (process.code_signature.trusted == true and not process.code_signature.subject_name : "Microsoft *") and 
113   not (process.name : "powershell.exe" and process.args : "?:\\ProgramData\\Microsoft\\Windows Defender Advanced Threat Protection\\Downloads\\PSScript_*.ps1")]
114  [network where host.os.type == "windows" and destination.port == 445 and process.pid != 4 and
115     not cidrmatch(destination.ip, "127.0.0.1", "::1")]
116until [process where host.os.type == "windows" and event.type == "end"]
117'''
118
119
120[[rule.threat]]
121framework = "MITRE ATT&CK"
122[[rule.threat.technique]]
123id = "T1021"
124name = "Remote Services"
125reference = "https://attack.mitre.org/techniques/T1021/"
126[[rule.threat.technique.subtechnique]]
127id = "T1021.002"
128name = "SMB/Windows Admin Shares"
129reference = "https://attack.mitre.org/techniques/T1021/002/"
130
131
132
133[rule.threat.tactic]
134id = "TA0008"
135name = "Lateral Movement"
136reference = "https://attack.mitre.org/tactics/TA0008/"