Jonhnathan
106 lines
4.5 KiB
TOML
106 lines
4.5 KiB
TOML
[metadata]
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creation_date = "2020/11/30"
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maturity = "production"
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updated_date = "2022/04/13"
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[rule]
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author = ["Elastic"]
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description = "Identifies powershell.exe being used to download an executable file from an untrusted remote destination."
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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 PowerShell"
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note = """## Triage and analysis
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### Investigating Remote File Download via PowerShell
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Attackers commonly transfer tooling or malware from external systems into a compromised environment using the command
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and control channel. However, they can also abuse signed utilities to drop these files.
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PowerShell is one of system administrators' main tools for automation, report routines, and other tasks. This makes it
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available for use in various environments and creates an attractive way for attackers to execute code and perform
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actions. This rule correlates network and file events to detect downloads of executable and script files performed using
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PowerShell.
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#### Possible investigation steps
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- Investigate the process execution chain (parent process tree).
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- Identify the user account that performed the action and whether it should perform this kind of action.
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- Consider whether the user needs PowerShell to complete its tasks.
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- Investigate other alerts associated with the user/host during the past 48 hours.
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- Check the reputation of the domain or IP address used to host the downloaded file.
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- Retrieve the file and determine if it is 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 SHA-256 hash value of the file.
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- Search for the existence and reputation of this file in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
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### False positive analysis
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- Administrators can use PowerShell legitimately to download executable and script files. Analysts can dismiss the alert
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if the Administrator is aware of the activity and the triage has not identified suspicious or malicious files.
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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 any temporary network rules, procedures, and segmentation required to contain the malware.
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- Immediately block the IoCs identified.
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- Remove and block malicious artifacts identified on the triage.
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- Disable the involved accounts, or restrict their ability to log on remotely.
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- Reset passwords for the user account and other potentially compromised accounts (email, services, CRMs, etc.).
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- Investigate the initial attack vector.
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"""
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risk_score = 47
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rule_id = "33f306e8-417c-411b-965c-c2812d6d3f4d"
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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 with maxspan=30s
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[network where process.name : ("powershell.exe", "pwsh.exe", "powershell_ise.exe") and network.protocol == "dns" and
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not dns.question.name : ("localhost", "*.microsoft.com", "*.azureedge.net", "*.powershellgallery.com", "*.windowsupdate.com", "metadata.google.internal") and
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not user.domain : "NT AUTHORITY"]
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[file where process.name : "powershell.exe" and event.type == "creation" and file.extension : ("exe", "dll", "ps1", "bat") and
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not file.name : "__PSScriptPolicy*.ps1"]
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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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[[rule.threat]]
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framework = "MITRE ATT&CK"
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[[rule.threat.technique]]
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id = "T1059"
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name = "Command and Scripting Interpreter"
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reference = "https://attack.mitre.org/techniques/T1059/"
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[[rule.threat.technique.subtechnique]]
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id = "T1059.001"
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name = "PowerShell"
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reference = "https://attack.mitre.org/techniques/T1059/001/"
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[rule.threat.tactic]
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id = "TA0002"
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name = "Execution"
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reference = "https://attack.mitre.org/tactics/TA0002/"
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