Potential Foxmail Exploitation

  1[metadata]
  2creation_date = "2024/08/29"
  3integration = ["endpoint", "windows", "system", "sentinel_one_cloud_funnel", "m365_defender", "crowdstrike"]
  4maturity = "production"
  5min_stack_comments = "Breaking change at 8.14.0 for the Windows Integration."
  6min_stack_version = "8.14.0"
  7updated_date = "2025/01/15"
  8
  9[rule]
 10author = ["Elastic"]
 11description = """
 12Identifies the Foxmail client spawning a child process with argument pointing to the Foxmail temp directory.
 13This may indicate the successful exploitation of a Foxmail vulnerability for initial access and execution via
 14a malicious email.
 15"""
 16from = "now-9m"
 17index = [
 18    "winlogbeat-*",
 19    "logs-windows.*",
 20    "endgame-*",
 21    "logs-system.security*",
 22    "logs-windows.sysmon_operational-*",
 23    "logs-sentinel_one_cloud_funnel.*",
 24    "logs-m365_defender.event-*",
 25    "logs-endpoint.events.process-*",
 26    "logs-crowdstrike.fdr*"
 27]
 28language = "eql"
 29license = "Elastic License v2"
 30name = "Potential Foxmail Exploitation"
 31references = ["https://mp.weixin.qq.com/s/F8hNyESBdKhwXkQPgtGpew"]
 32risk_score = 73
 33rule_id = "2c6a6acf-0dcb-404d-89fb-6b0327294cfa"
 34severity = "high"
 35tags = [
 36    "Domain: Endpoint",
 37    "OS: Windows",
 38    "Use Case: Threat Detection",
 39    "Tactic: Initial Access",
 40    "Tactic: Execution",
 41    "Data Source: Elastic Defend",
 42    "Data Source: Sysmon",
 43    "Data Source: System",
 44    "Data Source: Elastic Endgame",
 45    "Data Source: SentinelOne",
 46    "Data Source: Microsoft Defender for Endpoint",
 47    "Data Source: Crowdstrike",
 48    "Resources: Investigation Guide"
 49]
 50timestamp_override = "event.ingested"
 51type = "eql"
 52
 53query = '''
 54process where host.os.type == "windows" and event.type == "start" and
 55 process.parent.name : "Foxmail.exe" and process.args : ("?:\\Users\\*\\AppData\\*", "\\\\*")
 56'''
 57note = """## Triage and analysis
 58
 59> **Disclaimer**:
 60> This investigation guide was created using generative AI technology and has been reviewed to improve its accuracy and relevance. While every effort has been made to ensure its quality, we recommend validating the content and adapting it to suit your specific environment and operational needs.
 61
 62### Investigating Potential Foxmail Exploitation
 63
 64Foxmail, a popular email client, can be exploited by adversaries to gain initial access and execute malicious payloads. Attackers may leverage vulnerabilities to spawn child processes from Foxmail, directing them to temporary directories where malicious files reside. The detection rule identifies such suspicious activities by monitoring process creation events, specifically when Foxmail spawns processes with arguments pointing to its temp directory, indicating potential exploitation attempts.
 65
 66### Possible investigation steps
 67
 68- Review the process creation event details to confirm that Foxmail.exe is the parent process and check the specific child process that was spawned.
 69- Examine the arguments of the spawned process to verify if they point to a suspicious temporary directory, as indicated by the query pattern (e.g., paths under "?:\\Users\\*\\AppData\\*").
 70- Investigate the contents of the identified temporary directory for any unusual or malicious files that may have been executed.
 71- Check the email logs and Foxmail client activity to identify any recent emails that could have contained malicious attachments or links leading to the exploitation attempt.
 72- Correlate the event with other security alerts or logs from data sources like Elastic Defend, Sysmon, or Microsoft Defender for Endpoint to identify any related suspicious activities or patterns.
 73- Assess the risk and impact on the affected system by determining if any unauthorized changes or additional malicious processes have been initiated following the initial alert.
 74
 75### False positive analysis
 76
 77- Routine software updates or installations may cause Foxmail to spawn child processes in the temp directory. Users can create exceptions for known update processes to prevent false alerts.
 78- Legitimate plugins or extensions for Foxmail might execute processes from the temp directory. Verify the legitimacy of these plugins and exclude them if they are trusted.
 79- Automated scripts or backup software interacting with Foxmail could trigger the rule. Identify these scripts and add them to an exclusion list if they are verified as safe.
 80- User-initiated actions such as importing or exporting data in Foxmail might result in temporary process creation. Monitor these activities and exclude them if they are part of regular operations.
 81- Security software performing scans or checks on Foxmail's temp directory can be mistaken for exploitation attempts. Confirm these activities and whitelist the security software processes involved.
 82
 83### Response and remediation
 84
 85- Isolate the affected system from the network to prevent further spread of the potential threat and to contain any ongoing malicious activity.
 86- Terminate any suspicious processes spawned by Foxmail that are identified in the alert to stop the execution of potentially malicious payloads.
 87- Conduct a thorough scan of the affected system using an updated antivirus or endpoint detection and response (EDR) tool to identify and remove any malicious files or remnants.
 88- Review and analyze email logs and quarantine any suspicious emails that may have been the source of the exploit to prevent further exploitation attempts.
 89- Apply any available security patches or updates to Foxmail and the operating system to mitigate known vulnerabilities and prevent future exploitation.
 90- Monitor the network and systems for any signs of lateral movement or additional compromise, using indicators of compromise (IOCs) identified during the investigation.
 91- Escalate the incident to the security operations center (SOC) or incident response team for further analysis and to determine if additional actions are required based on the scope and impact of the threat."""
 92
 93
 94[[rule.threat]]
 95framework = "MITRE ATT&CK"
 96[[rule.threat.technique]]
 97id = "T1203"
 98name = "Exploitation for Client Execution"
 99reference = "https://attack.mitre.org/techniques/T1203/"
100
101
102[rule.threat.tactic]
103id = "TA0002"
104name = "Execution"
105reference = "https://attack.mitre.org/tactics/TA0002/"
106[[rule.threat]]
107framework = "MITRE ATT&CK"
108[[rule.threat.technique]]
109id = "T1189"
110name = "Drive-by Compromise"
111reference = "https://attack.mitre.org/techniques/T1189/"
112
113
114[rule.threat.tactic]
115id = "TA0001"
116name = "Initial Access"
117reference = "https://attack.mitre.org/tactics/TA0001/"