Justin Ibarra
46d5e37b76
* min_stack all rules to 8.3 * bump date Co-authored-by: Mika Ayenson <mika.ayenson@elastic.co>
85 lines
3.4 KiB
TOML
85 lines
3.4 KiB
TOML
[metadata]
|
|
creation_date = "2021/03/04"
|
|
maturity = "production"
|
|
min_stack_comments = "New fields added: required_fields, related_integrations, setup"
|
|
min_stack_version = "8.3.0"
|
|
updated_date = "2022/08/24"
|
|
|
|
[rule]
|
|
author = ["Elastic", "Austin Songer"]
|
|
description = """
|
|
Identifies suspicious files being written by the Microsoft Exchange Server Unified Messaging (UM) service. This activity
|
|
has been observed exploiting CVE-2021-26858.
|
|
"""
|
|
false_positives = [
|
|
"""
|
|
Files generated during installation will generate a lot of noise, so the rule should only be enabled after the fact.
|
|
""",
|
|
"""
|
|
This rule was tuned using the following baseline:
|
|
https://raw.githubusercontent.com/microsoft/CSS-Exchange/main/Security/Baselines/baseline_15.2.792.5.csv from
|
|
Microsoft. Depending on version, consult https://github.com/microsoft/CSS-Exchange/tree/main/Security/Baselines to
|
|
help determine normalcy.
|
|
""",
|
|
]
|
|
from = "now-9m"
|
|
index = ["winlogbeat-*", "logs-endpoint.events.*", "logs-windows.*"]
|
|
language = "eql"
|
|
license = "Elastic License v2"
|
|
name = "Microsoft Exchange Server UM Writing Suspicious Files"
|
|
note = """## Triage and analysis
|
|
|
|
Positive hits can be checked against the established Microsoft [baselines](https://github.com/microsoft/CSS-Exchange/tree/main/Security/Baselines).
|
|
|
|
Microsoft highly recommends that the best course of action is patching, but this may not protect already compromised systems
|
|
from existing intrusions. Other tools for detecting and mitigating can be found within their Exchange support
|
|
[repository](https://github.com/microsoft/CSS-Exchange/tree/main/Security)
|
|
|
|
|
|
## Setup
|
|
|
|
If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.
|
|
"""
|
|
references = [
|
|
"https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers",
|
|
"https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities",
|
|
]
|
|
risk_score = 47
|
|
rule_id = "6cd1779c-560f-4b68-a8f1-11009b27fe63"
|
|
severity = "medium"
|
|
tags = ["Elastic", "Host", "Windows", "Threat Detection", "Initial Access"]
|
|
timestamp_override = "event.ingested"
|
|
type = "eql"
|
|
|
|
query = '''
|
|
file where event.type == "creation" and
|
|
process.name : ("UMWorkerProcess.exe", "umservice.exe") and
|
|
file.extension : ("php", "jsp", "js", "aspx", "asmx", "asax", "cfm", "shtml") and
|
|
(
|
|
file.path : "?:\\inetpub\\wwwroot\\aspnet_client\\*" or
|
|
|
|
(file.path : "?:\\*\\Microsoft\\Exchange Server*\\FrontEnd\\HttpProxy\\owa\\auth\\*" and
|
|
not (file.path : "?:\\*\\Microsoft\\Exchange Server*\\FrontEnd\\HttpProxy\\owa\\auth\\version\\*" or
|
|
file.name : ("errorFE.aspx", "expiredpassword.aspx", "frowny.aspx", "GetIdToken.htm", "logoff.aspx",
|
|
"logon.aspx", "OutlookCN.aspx", "RedirSuiteServiceProxy.aspx", "signout.aspx"))) or
|
|
|
|
(file.path : "?:\\*\\Microsoft\\Exchange Server*\\FrontEnd\\HttpProxy\\ecp\\auth\\*" and
|
|
not file.name : "TimeoutLogoff.aspx")
|
|
)
|
|
'''
|
|
|
|
|
|
[[rule.threat]]
|
|
framework = "MITRE ATT&CK"
|
|
[[rule.threat.technique]]
|
|
id = "T1190"
|
|
name = "Exploit Public-Facing Application"
|
|
reference = "https://attack.mitre.org/techniques/T1190/"
|
|
|
|
|
|
[rule.threat.tactic]
|
|
id = "TA0001"
|
|
name = "Initial Access"
|
|
reference = "https://attack.mitre.org/tactics/TA0001/"
|
|
|