Command Prompt Network Connection

  1[metadata]
  2creation_date = "2020/02/18"
  3integration = ["endpoint", "windows"]
  4maturity = "production"
  5updated_date = "2025/03/20"
  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 cmd.exe making a network connection. Adversaries could abuse cmd.exe to download or execute malware from a
 37remote URL.
 38"""
 39false_positives = [
 40    """
 41    Administrators may use the command prompt for regular administrative tasks. It's important to baseline your
 42    environment for network connections being made from the command prompt to determine any abnormal use of this tool.
 43    """,
 44]
 45from = "now-9m"
 46index = [
 47    "winlogbeat-*",
 48    "logs-endpoint.events.process-*",
 49    "logs-endpoint.events.network-*",
 50    "logs-windows.sysmon_operational-*",
 51]
 52language = "eql"
 53license = "Elastic License v2"
 54name = "Command Prompt Network Connection"
 55note = """## Triage and analysis
 56
 57### Investigating Command Prompt Network Connection
 58
 59Attackers commonly transfer tooling or malware from external systems into a compromised environment using a command and control channel. However, they can also abuse signed utilities to drop these files.
 60
 61This rule looks for a network connection to an external address from the `cmd.exe` utility, which can indicate the abuse of the utility to download malicious files and tools.
 62
 63> **Note**:
 64> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/current/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 65
 66#### Possible investigation steps
 67
 68- Investigate other alerts associated with the user/host during the past 48 hours.
 69- 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.
 70  - Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications, and any spawned child processes.
 71  - Investigate the file digital signature and process original filename, if suspicious, treat it as potential malware.
 72- Investigate the target host that the signed binary is communicating with.
 73  - Check if the domain is newly registered or unexpected.
 74  - Check the reputation of the domain or IP address.
 75- Examine if any file was downloaded and check if it is an executable or script.
 76- Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
 77- Examine the host for derived artifacts that indicate suspicious activities:
 78  - Analyze the downloaded file using a private sandboxed analysis system.
 79  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
 80    - Attempts to contact external domains and addresses.
 81      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
 82      - Examine the DNS cache for suspicious or anomalous entries.
 83        - $osquery_0
 84    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
 85    - Examine the host services for suspicious or anomalous entries.
 86      - $osquery_1
 87      - $osquery_2
 88      - $osquery_3
 89  - 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.
 90
 91### False positive analysis
 92
 93- If this activity is expected and noisy in your environment, consider adding exceptions — preferably with a combination of destination IP address and file name conditions.
 94
 95### Response and remediation
 96
 97- Initiate the incident response process based on the outcome of the triage.
 98- Isolate the involved host to prevent further post-compromise behavior.
 99- If the triage identified malware, search the environment for additional compromised hosts.
100  - Implement temporary network rules, procedures, and segmentation to contain the malware.
101  - Stop suspicious processes.
102  - Immediately block the identified indicators of compromise (IoCs).
103  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
104- Remove and block malicious artifacts identified during triage.
105- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
106- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
107- 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).
108"""
109references = ["https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml"]
110risk_score = 21
111rule_id = "89f9a4b0-9f8f-4ee0-8823-c4751a6d6696"
112severity = "low"
113tags = [
114    "Domain: Endpoint",
115    "OS: Windows",
116    "Use Case: Threat Detection",
117    "Tactic: Execution",
118    "Resources: Investigation Guide",
119    "Data Source: Elastic Defend",
120    "Data Source: Sysmon",
121]
122type = "eql"
123
124query = '''
125sequence by process.entity_id
126  [process where host.os.type == "windows" and process.name : "cmd.exe" and event.type == "start"]
127  [network where host.os.type == "windows" and process.name : "cmd.exe" and
128     not cidrmatch(destination.ip, "10.0.0.0/8", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12", "192.0.0.0/24",
129                                  "192.0.0.0/29", "192.0.0.8/32", "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32",
130                                  "192.0.0.171/32", "192.0.2.0/24", "192.31.196.0/24", "192.52.193.0/24",
131                                  "192.168.0.0/16", "192.88.99.0/24", "224.0.0.0/4", "100.64.0.0/10", "192.175.48.0/24",
132                                  "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1",
133                                  "FE80::/10", "FF00::/8") and
134    not dns.question.name : (
135          "wpad", "localhost", "ocsp.comodoca.com", "ocsp.digicert.com", "ocsp.sectigo.com", "crl.comodoca.com"
136    )]
137'''
138
139
140[[rule.threat]]
141framework = "MITRE ATT&CK"
142[[rule.threat.technique]]
143id = "T1059"
144name = "Command and Scripting Interpreter"
145reference = "https://attack.mitre.org/techniques/T1059/"
146
147
148[rule.threat.tactic]
149id = "TA0002"
150name = "Execution"
151reference = "https://attack.mitre.org/tactics/TA0002/"
152[[rule.threat]]
153framework = "MITRE ATT&CK"
154[[rule.threat.technique]]
155id = "T1105"
156name = "Ingress Tool Transfer"
157reference = "https://attack.mitre.org/techniques/T1105/"
158
159
160[rule.threat.tactic]
161id = "TA0011"
162name = "Command and Control"
163reference = "https://attack.mitre.org/tactics/TA0011/"