Justin Ibarra
78 lines
3.0 KiB
TOML
78 lines
3.0 KiB
TOML
[metadata]
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creation_date = "2021/03/04"
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maturity = "production"
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updated_date = "2021/05/10"
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[rule]
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author = ["Elastic", "Austin Songer"]
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description = """
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Identifies suspicious files being written by the Microsoft Exchange Server Unified Messaging (UM) service. This activity
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has been observed exploiting CVE-2021-26858.
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"""
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false_positives = [
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"""
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Files generated during installation will generate a lot of noise, so the rule should only be enabled after the fact.
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""",
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"""
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This rule was tuned using the following baseline:
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https://raw.githubusercontent.com/microsoft/CSS-Exchange/main/Security/Baselines/baseline_15.2.792.5.csv from
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Microsoft. Depending on version, consult https://github.com/microsoft/CSS-Exchange/tree/main/Security/Baselines to
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help determine normalcy.
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""",
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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 = "Microsoft Exchange Server UM Writing Suspicious Files"
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note = """## Triage and analysis
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Positive hits can be checked against the established Microsoft [baselines](https://github.com/microsoft/CSS-Exchange/tree/main/Security/Baselines).
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Microsoft highly recommends that the best course of action is patching, but this may not protect already compromised systems
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from existing intrusions. Other tools for detecting and mitigating can be found within their Exchange support
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[repository](https://github.com/microsoft/CSS-Exchange/tree/main/Security)
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"""
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references = [
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"https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers",
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"https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities",
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]
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risk_score = 47
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rule_id = "6cd1779c-560f-4b68-a8f1-11009b27fe63"
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severity = "medium"
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tags = ["Elastic", "Host", "Windows", "Threat Detection", "Initial Access"]
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timestamp_override = "event.ingested"
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type = "eql"
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query = '''
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file where event.type == "creation" and
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process.name : ("UMWorkerProcess.exe", "umservice.exe") and
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file.extension : ("php", "jsp", "js", "aspx", "asmx", "asax", "cfm", "shtml") and
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(
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file.path : "?:\\inetpub\\wwwroot\\aspnet_client\\*" or
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(file.path : "?:\\*\\Microsoft\\Exchange Server*\\FrontEnd\\HttpProxy\\owa\\auth\\*" and
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not (file.path : "?:\\*\\Microsoft\\Exchange Server*\\FrontEnd\\HttpProxy\\owa\\auth\\version\\*" or
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file.name : ("errorFE.aspx", "expiredpassword.aspx", "frowny.aspx", "GetIdToken.htm", "logoff.aspx",
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"logon.aspx", "OutlookCN.aspx", "RedirSuiteServiceProxy.aspx", "signout.aspx"))) or
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(file.path : "?:\\*\\Microsoft\\Exchange Server*\\FrontEnd\\HttpProxy\\ecp\\auth\\*" and
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not file.name : "TimeoutLogoff.aspx")
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)
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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 = "T1190"
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name = "Exploit Public-Facing Application"
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reference = "https://attack.mitre.org/techniques/T1190/"
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[rule.threat.tactic]
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id = "TA0001"
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name = "Initial Access"
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reference = "https://attack.mitre.org/tactics/TA0001/"
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