Splunk Security
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The following analytic detects the deletion of critical directories on a Linux machine using the `rm` command with argument rf. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions targeting directories like /boot, /var/log, /etc, and /dev. This activity is significant because deleting these directories can severely disrupt system operations and is often associated with destructive campaigns like Industroyer2. If confirmed malicious, this action could lead to system instability, data loss, and potential downtime, making it crucial for immediate investigation and response.
The analytic detects the deletion of SSL certificates on a Linux machine. It leverages filesystem event logs to identify when files with extensions .pem or .crt are deleted from the /etc/ssl/certs/ directory. This activity is significant because attackers may delete or modify SSL certificates to disable security features or evade defenses on a compromised system. If confirmed malicious, this behavior could indicate an attempt to disrupt secure communications, evade detection, or execute a destructive payload, potentially leading to significant security breaches and data loss.
The following analytic identifies the execution of the 'pkill' command, which is used to terminate processes on a Linux system. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions. This activity is significant because threat actors often use 'pkill' to disable security defenses or terminate critical processes, facilitating further malicious actions. If confirmed malicious, this behavior could lead to the disruption of security applications, enabling attackers to evade detection and potentially corrupt or destroy files on the targeted system.
The analytic detects the use of 'curl' and 'wget' commands within a Linux environment. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names, user information, and command-line executions. This activity is significant as 'curl' and 'wget' are commonly used for downloading files, which can indicate potential ingress of malicious tools. If confirmed malicious, this activity could lead to unauthorized code execution, data exfiltration, or further compromise of the system. Monitoring and tuning this detection helps identify and differentiate between normal and potentially harmful usage.
The analytic detects the use of the base64 decode command on Linux systems, which is often used to deobfuscate files. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions that include "base64 -d" or "base64 --decode". This activity is significant as it may indicate an attempt to hide malicious payloads or scripts. If confirmed malicious, an attacker could use this technique to execute hidden code, potentially leading to unauthorized access, data exfiltration, or further system compromise.
The analytic identifies potential Linux persistence and privilege escalation activities by correlating risk scores and event counts from various Linux-related data sources. It focuses on behaviors associated with persistence and privilege escalation tactics. This activity is significant for a SOC because it highlights behaviors that could allow an attacker to maintain access or gain elevated privileges on a Linux system. If confirmed malicious, this activity could enable an attacker to execute code with higher privileges, persist in the environment, and potentially access sensitive information, posing a severe security risk.
The following analytic detects potential unauthorized modifications to Linux cronjobs using text editors like "nano," "vi," or "vim." It identifies this activity by monitoring command-line executions that interact with cronjob configuration paths. This behavior is significant for a SOC as it may indicate attempts at privilege escalation or establishing persistent access. If confirmed malicious, the impact could be severe, allowing attackers to execute damaging actions such as data theft, system sabotage, or further network penetration.
The following analytic identifies the creation of suspicious .aspx files in specific directories associated with Exchange exploitation by the HAFNIUM group and the ProxyShell vulnerability. It detects this activity by monitoring the MSExchangeMailboxReplication.exe process, which typically does not write .aspx files. This behavior is significant as it may indicate an active exploitation attempt on Exchange servers. If confirmed malicious, attackers could gain unauthorized access, execute arbitrary code, or maintain persistence within the environment. Immediate investigation and remediation are crucial to prevent further compromise.
The following analytic detects the suspicious creation of msmpeng.exe or mpsvc.dll in non-default Windows Defender folders. It leverages the Endpoint.Filesystem datamodel to identify instances where these files are created outside their expected directories. This activity is significant because it is associated with the REvil ransomware, which uses DLL side-loading to execute malicious payloads. If confirmed malicious, this could lead to ransomware deployment, resulting in data encryption, system compromise, and potential data loss or extortion.
This analytic detects the execution of a COM CLSID through PowerShell. It specifically looks for PowerShell script block logs (EventCode 4104) containing the string "*CreateInstance([type]::GetTypeFromCLSID*". This activity is significant because adversaries and malware, such as Conti ransomware, commonly use COM object creation via PowerShell for purposes like privilege escalation or bypassing User Account Control (UAC). Successful exploitation of this technique could lead to elevated privileges or persistence within the environment, posing a significant security risk.
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