Justin Ibarra
46d5e37b76
* min_stack all rules to 8.3 * bump date Co-authored-by: Mika Ayenson <mika.ayenson@elastic.co>
102 lines
4.8 KiB
TOML
102 lines
4.8 KiB
TOML
[metadata]
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creation_date = "2020/11/29"
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maturity = "production"
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min_stack_comments = "New fields added: required_fields, related_integrations, setup"
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min_stack_version = "8.3.0"
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updated_date = "2022/08/24"
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[rule]
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author = ["Elastic"]
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description = """
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Identifies built-in Windows script interpreters (cscript.exe or wscript.exe) being used to download an executable file
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from a remote destination.
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"""
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from = "now-9m"
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index = ["winlogbeat-*", "logs-endpoint.events.*", "logs-windows.*"]
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language = "eql"
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license = "Elastic License v2"
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name = "Remote File Download via Script Interpreter"
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note = """## Triage and analysis
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### Investigating Remote File Download via Script Interpreter
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The Windows Script Host (WSH) is a Windows automation technology, which is ideal for non-interactive scripting needs,
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such as logon scripting, administrative scripting, and machine automation.
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Attackers commonly use WSH scripts as their initial access method, acting like droppers for second stage payloads, but
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can also use them to download tools and utilities needed to accomplish their goals.
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This rule looks for DLLs and executables downloaded using `cscript.exe` or `wscript.exe`.
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#### Possible investigation steps
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- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files
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for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
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- Retrieve the script file and the executable involved and determine if they are malicious:
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- Use a private sandboxed malware analysis system to perform analysis.
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- Observe and collect information about the following activities:
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- Attempts to contact external domains and addresses.
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- File and registry access, modification, and creation activities.
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- Service creation and launch activities.
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- Scheduled tasks creation.
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- Use the PowerShell Get-FileHash cmdlet to get the files' SHA-256 hash values.
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- Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
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- Manually analyze the script to determine if malicious capabilities are present.
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- Investigate whether the potential malware ran successfully, is active on the host, or was stopped by defenses.
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- Investigate other alerts associated with the user/host during the past 48 hours.
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- Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
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### False positive analysis
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- The usage of these script engines by regular users is unlikely. In the case of authorized benign true positives
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(B-TPs), exceptions can be added.
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### Response and remediation
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- Initiate the incident response process based on the outcome of the triage.
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- Isolate the involved host to prevent further post-compromise behavior.
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- If the triage identified malware, search the environment for additional compromised hosts.
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- Implement temporary network rules, procedures, and segmentation to contain the malware.
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- Stop suspicious processes.
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- Immediately block the identified indicators of compromise (IoCs).
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- Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that
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attackers could use to reinfect the system.
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- Remove and block malicious artifacts identified during triage.
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- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
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malware components.
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- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are
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identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business
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systems, and web services.
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- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
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- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
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mean time to respond (MTTR).
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"""
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risk_score = 47
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rule_id = "1d276579-3380-4095-ad38-e596a01bc64f"
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severity = "medium"
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tags = ["Elastic", "Host", "Windows", "Threat Detection", "Command and Control"]
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type = "eql"
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query = '''
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sequence by host.id, process.entity_id
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[network where process.name : ("wscript.exe", "cscript.exe") and network.protocol != "dns" and
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network.direction : ("outgoing", "egress") and network.type == "ipv4" and destination.ip != "127.0.0.1"
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]
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[file where event.type == "creation" and file.extension : ("exe", "dll")]
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'''
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[[rule.threat]]
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framework = "MITRE ATT&CK"
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[[rule.threat.technique]]
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id = "T1105"
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name = "Ingress Tool Transfer"
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reference = "https://attack.mitre.org/techniques/T1105/"
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[rule.threat.tactic]
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id = "TA0011"
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name = "Command and Control"
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reference = "https://attack.mitre.org/tactics/TA0011/"
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