Jonhnathan
107 lines
4.6 KiB
TOML
107 lines
4.6 KiB
TOML
[metadata]
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creation_date = "2020/02/18"
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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 = "2022/10/11"
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[rule]
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author = ["Elastic"]
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description = "Identifies suspicious commands executed via a web server, which may suggest a vulnerability and remote shell access."
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false_positives = [
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"""
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Network monitoring or management products may have a web server component that runs shell commands as part of normal
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behavior.
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""",
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]
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from = "now-9m"
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index = ["auditbeat-*", "logs-endpoint.events.*"]
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language = "kuery"
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license = "Elastic License v2"
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name = "Potential Shell via Web Server"
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note = """## Triage and analysis
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### Investigating Potential Shell via Web Server
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Adversaries may backdoor web servers with web shells to establish persistent access to systems. A web shell is a web
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script that is placed on an openly accessible web server to allow an adversary to use the web server as a gateway into a
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network. A web shell may provide a set of functions to execute or a command line interface on the system that hosts the
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web server.
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This rule detects a web server process spawning script and command line interface programs, potentially indicating
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attackers executing commands using the web shell.
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#### Possible investigation steps
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- Investigate abnormal behaviors observed by the subject process such as network connections, file modifications, and
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any other spawned child processes.
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- Examine the command line to determine which commands or scripts were executed.
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- Investigate other alerts associated with the user/host during the past 48 hours.
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- If scripts or executables were dropped, retrieve the files 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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- Check if the domain is newly registered or unexpected.
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- Check the reputation of the domain or IP address.
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- File access, modification, and creation activities.
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- Cron jobs, services and other persistence mechanisms.
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### False positive analysis
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- This activity is unlikely to happen legitimately. Any activity that triggered the alert and is not inherently
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malicious must be monitored by the security team.
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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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- 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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- 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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- 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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references = ["https://pentestlab.blog/tag/web-shell/"]
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risk_score = 47
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rule_id = "231876e7-4d1f-4d63-a47c-47dd1acdc1cb"
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severity = "medium"
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tags = ["Elastic", "Host", "Linux", "Threat Detection", "Persistence", "has_guide"]
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timestamp_override = "event.ingested"
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type = "query"
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query = '''
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event.category:process and event.type:(start or process_started) and
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process.name:(bash or dash or ash or zsh or "python*" or "perl*" or "php*") and
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process.parent.name:("apache" or "nginx" or "www" or "apache2" or "httpd" or "www-data")
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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 = "T1505"
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name = "Server Software Component"
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reference = "https://attack.mitre.org/techniques/T1505/"
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[[rule.threat.technique.subtechnique]]
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id = "T1505.003"
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name = "Web Shell"
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reference = "https://attack.mitre.org/techniques/T1505/003/"
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[rule.threat.tactic]
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id = "TA0003"
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name = "Persistence"
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reference = "https://attack.mitre.org/tactics/TA0003/"
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