Network Connection via Signed Binary

  1[metadata]
  2creation_date = "2020/02/18"
  3integration = ["endpoint", "windows"]
  4maturity = "production"
  5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
  6min_stack_version = "8.3.0"
  7updated_date = "2024/04/08"
  8
  9[transform]
 10[[transform.osquery]]
 11label = "Osquery - Retrieve DNS Cache"
 12query = "SELECT * FROM dns_cache"
 13
 14[[transform.osquery]]
 15label = "Osquery - Retrieve All Services"
 16query = "SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services"
 17
 18[[transform.osquery]]
 19label = "Osquery - Retrieve Services Running on User Accounts"
 20query = """
 21SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services WHERE
 22NOT (user_account LIKE '%LocalSystem' OR user_account LIKE '%LocalService' OR user_account LIKE '%NetworkService' OR
 23user_account == null)
 24"""
 25
 26[[transform.osquery]]
 27label = "Osquery - Retrieve Service Unsigned Executables with Virustotal Link"
 28query = """
 29SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, name, description, start_type, status, pid,
 30services.path FROM services JOIN authenticode ON services.path = authenticode.path OR services.module_path =
 31authenticode.path JOIN hash ON services.path = hash.path WHERE authenticode.result != 'trusted'
 32"""
 33
 34[rule]
 35author = ["Elastic"]
 36description = """
 37Binaries signed with trusted digital certificates can execute on Windows systems protected by digital signature
 38validation. Adversaries may use these binaries to 'live off the land' and execute malicious files that could bypass
 39application allowlists and signature validation.
 40"""
 41from = "now-9m"
 42index = ["winlogbeat-*", "logs-endpoint.events.process-*", "logs-endpoint.events.network-*", "logs-windows.sysmon_operational-*"]
 43language = "eql"
 44license = "Elastic License v2"
 45name = "Network Connection via Signed Binary"
 46note = """## Triage and analysis
 47
 48### Investigating Network Connection via Signed Binary
 49
 50By examining the specific traits of Windows binaries (such as process trees, command lines, network connections, registry modifications, and so on) it's possible to establish a baseline of normal activity. Deviations from this baseline can indicate malicious activity, such as masquerading and deserve further investigation.
 51
 52This rule looks for the execution of `expand.exe`, `extrac32.exe`, `ieexec.exe`, or `makecab.exe` utilities, followed by a network connection to an external address. Attackers can abuse utilities to execute malicious files or masquerade as those utilities to bypass detections and evade defenses.
 53
 54> **Note**:
 55> 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.
 56
 57#### Possible investigation steps
 58
 59- Investigate other alerts associated with the user/host during the past 48 hours.
 60- 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.
 61  - Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications, and any spawned child processes.
 62  - Investigate the file digital signature and process original filename, if suspicious, treat it as potential malware.
 63- Investigate the target host that the signed binary is communicating with.
 64  - Check if the domain is newly registered or unexpected.
 65  - Check the reputation of the domain or IP address.
 66- Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
 67- Examine the host for derived artifacts that indicate suspicious activities:
 68  - Analyze the process executable using a private sandboxed analysis system.
 69  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
 70    - Attempts to contact external domains and addresses.
 71      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
 72      - Examine the DNS cache for suspicious or anomalous entries.
 73        - $osquery_0
 74    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
 75    - Examine the host services for suspicious or anomalous entries.
 76      - $osquery_1
 77      - $osquery_2
 78      - $osquery_3
 79  - 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.
 80
 81### False positive analysis
 82
 83- If this activity is expected and noisy in your environment, consider adding exceptions — preferably with a combination of destination IP address and command line conditions.
 84
 85### Response and remediation
 86
 87- Initiate the incident response process based on the outcome of the triage.
 88- Isolate the involved host to prevent further post-compromise behavior.
 89- If the triage identified malware, search the environment for additional compromised hosts.
 90  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 91  - Stop suspicious processes.
 92  - Immediately block the identified indicators of compromise (IoCs).
 93  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
 94- Remove and block malicious artifacts identified during triage.
 95- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 96- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 97- 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).
 98"""
 99references = ["https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml"]
100risk_score = 21
101rule_id = "63e65ec3-43b1-45b0-8f2d-45b34291dc44"
102severity = "low"
103tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Defense Evasion", "Resources: Investigation Guide", "Data Source: Elastic Defend", "Data Source: Sysmon"]
104type = "eql"
105
106query = '''
107sequence by process.entity_id
108  [process where host.os.type == "windows" and (process.name : "expand.exe" or process.name : "extrac32.exe" or
109                 process.name : "ieexec.exe" or process.name : "makecab.exe") and
110                 event.type == "start"]
111  [network where host.os.type == "windows" and (process.name : "expand.exe" or process.name : "extrac32.exe" or
112                 process.name : "ieexec.exe" or process.name : "makecab.exe") and
113    not cidrmatch(destination.ip,
114      "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", "192.0.0.0/29", "192.0.0.8/32",
115      "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24", "192.31.196.0/24",
116      "192.52.193.0/24", "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",
117      "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1", "FE80::/10", "FF00::/8")]
118'''
119
120
121[[rule.threat]]
122framework = "MITRE ATT&CK"
123[[rule.threat.technique]]
124id = "T1218"
125name = "System Binary Proxy Execution"
126reference = "https://attack.mitre.org/techniques/T1218/"
127
128
129[rule.threat.tactic]
130id = "TA0005"
131name = "Defense Evasion"
132reference = "https://attack.mitre.org/tactics/TA0005/"