Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
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The following analytic detects the abnormal termination of the Linux audit daemon (auditd) by identifying DAEMON_ABORT events in audit logs. These terminations suggest a serious failure of the auditing subsystem, potentially due to resource exhaustion, corruption, or malicious interference. Unlike a clean shutdown, DAEMON_ABORT implies that audit logging may have been disabled without system administrator intent. Alerts should be generated on detection and correlated with DAEMON_START, DAEMON_END, and system logs to determine root cause. If no DAEMON_START follows soon after, or this pattern repeats, it indicates a high-severity issue that impacts log integrity and should be immediately investigated.
The following analytic detects the (re)initialization of the Linux audit daemon (auditd) by identifying log entries of type DAEMON_START. This event indicates that the audit subsystem has resumed logging after being stopped or has started during system boot. While DAEMON_START may be expected during reboots or legitimate configuration changes, it can also signal attempts to re-enable audit logging after evasion, or restarts with modified or reduced rule sets. Monitoring this event in correlation with DAEMON_END, DAEMON_ABORT, and auditctl activity provides visibility into the continuity and integrity of audit logs. Frequent or unexplained DAEMON_START events should be investigated, especially if they are not accompanied by valid administrative or system activity.
The following analytic detects the suspicious sysmon service stop. This behavior is critical for a SOC to monitor because it may indicate attempts to gain unauthorized access or maintain control over a system. Such actions could be signs of malicious activity. If confirmed, this could lead to serious consequences, including a compromised system, unauthorized access to sensitive data, or even a wider breach affecting the entire network. Detecting and responding to these signs early is essential to prevent potential security incidents.
The analytic detects suspicious access or modification of the sshd_config file on Linux systems. It leverages data from Linux Auditd, focusing on command-line executions involving processes like "cat," "nano," "vim," and "vi" accessing the sshd_config file. This activity is significant because unauthorized changes to sshd_config can allow threat actors to redirect port connections or use unauthorized keys, potentially compromising the system. If confirmed malicious, this could lead to unauthorized access, privilege escalation, or persistent backdoor access, posing a severe security risk.
The following analytic detects potential tampering with cronjob files on a Linux system by identifying 'echo' commands that append code to existing cronjob files. It leverages logs from Linux Auditd, focusing on process names, parent processes, and command-line executions. This activity is significant because adversaries often use it for persistence or privilege escalation. If confirmed malicious, this could allow attackers to execute unauthorized code automatically, leading to system compromises and unauthorized data access, thereby impacting business operations and data integrity.
The following analytic detects the creation of the doas.conf file on a Linux host. This file is used by the doas utility to allow standard users to perform tasks as root, similar to sudo. The detection leverages Linux Auditd data, focusing on the creation of the doas.conf file. This activity is significant because it can indicate an attempt to gain elevated privileges, potentially by an adversary. If confirmed malicious, this could allow an attacker to execute commands with root commands with root privileges, leading to full system compromise.
This analytic detects the suspicious disable or modification of system firewalls on Linux systems. Specifically, it looks for `SERVICE_STOP` events for `firewalld` or `ufw` units. This behavior is critical to monitor as it may indicate attempts to gain unauthorized access or maintain control over a system by bypassing network controls. Such actions could be signs of malicious activity, potentially leading to a compromised system, unauthorized access to sensitive data, or a wider network breach. Early detection and response are essential to prevent potential security incidents.
The analytic detects suspicious stopping of the `osquery` service, which may indicate an attempt to disable monitoring and evade detection. `Osquery` is a powerful tool used for querying system information and detecting anomalies, and stopping its service can be a sign that an attacker is trying to disrupt security monitoring or hide malicious activities. By monitoring for unusual or unauthorized stops of the `osquery` service, this analytic helps identify potential efforts to bypass security controls, enabling security teams to investigate and respond to possible threats effectively.
The following analytic detects suspicious preload hijacking via the `preload` file, which may indicate an attacker's attempt to intercept or manipulate library loading processes. The `preload` file can be used to force the loading of specific libraries before others, potentially allowing malicious code to execute or alter application behavior. By monitoring for unusual or unauthorized modifications to the `preload` file, this analytic helps identify attempts to hijack preload mechanisms, enabling security teams to investigate and address potential threats to system integrity and security.
This rule detects attempts to hijack the Amazon SSM Agent on Linux systems. Specifically, it looks for the 'amazon-ssm-agent' executable being run with command-line arguments indicative of registration with a new code, ID, and region. This behavior is consistent with the technique described in the Mitiga research report where the SSM agent can be abused as a remote access trojan for persistence and command and control.
Detects suspicious use of command-line tools such as curl or wget to download remote
content - particularly scripts - into temporary directories (e.g., /dev/shm, /tmp), followed by
immediate execution, indicating potential malicious activity. This pattern is commonly used
by malicious scripts, stagers, or downloaders in fileless or multi-stage Linux attacks.
content - particularly scripts - into temporary directories (e.g., /dev/shm, /tmp), followed by
immediate execution, indicating potential malicious activity. This pattern is commonly used
by malicious scripts, stagers, or downloaders in fileless or multi-stage Linux attacks.
The following analytic detects command-line activities that redirect stdout or stderr to the /dev/null file. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs. This behavior is significant as it can indicate attempts to hide command outputs, a technique observed in the CyclopsBlink malware to conceal modifications to iptables firewall settings. If confirmed malicious, this activity could allow an attacker to stealthily alter system configurations, potentially leading to unauthorized access or persistent control over the compromised machine.
The analytic identifies potential exploitation attempts on a PaperCut NG server by analyzing its debug log data. It detects unauthorized or suspicious access attempts from public IP addresses and searches for specific URIs associated with known exploits. The detection leverages regex to parse unstructured log data, focusing on admin login activities. This activity is significant as it can indicate an active exploitation attempt on the server. If confirmed malicious, attackers could gain unauthorized access, potentially leading to data breaches or further compromise of the server.
Detects the use of command-line tools such as 'scp', 'rsync', and 'sftp' that are commonly used to copy files to or from remote systems. This activity can be indicative of an adversary transferring tools into an environment (Ingress Tool Transfer) or moving files laterally within a compromised network (Lateral Tool Transfer). The rule specifically looks for the presence of these tool names followed by a space and then a colon or an '@' symbol, which are characteristic of remote file operations.
Detects the use of the `syslog` syscall with action codes 4, 5, or 6, which can clear or disable the kernel ring buffer (dmesg logs). This technique can be used by attackers to hide traces after exploitation or privilege escalation. A common method is running `dmesg -c`, which internally triggers this syscall.
This rule detects attempts to enumerate local system groups on Linux. Adversaries often perform this discovery technique to understand the environment and identify users with elevated permissions. The rule triggers on execution of the 'groups' command or on common file viewing utilities (cat, ed, head, less, more, nano, tail, vi, vim) when they are used to read the '/etc/group' file.
This rule detects the execution or creation of files identified as Remote Access Tools (RATs) based on a Google Cloud Threat Intelligence (GCTI) feed. It correlates process launch, module load, or file creation events with known SHA256 hashes of RATs provided by the GCTI feed. The rule specifically looks for events where the SHA256 hash of the process or file matches a hash from the 'Remote Access Tools' threat feed within the GCTI graph.
Detects the execution of common text-based file access or inspection utilities to read the content of the '/etc/sudoers' file on Linux systems. This activity is often performed by adversaries to discover users with sudo rights, which can be a precursor to privilege escalation.
Detects attempts to record audio using the `arecord` and `ecasound` utilities on Linux systems. This rule specifically looks for the execution of `arecord` with common audio recording flags (`-vv`, `-fdat`) or the `ecasound` utility making a `memfd_create` syscall, which could indicate audio processing or recording.
This rule detects when a file, identified as malicious by Google Safe Browsing, initiates an outbound network connection to an IP address known to be a Tor Exit Node, as identified by Google Cloud Threat Intelligence (GCTI) Feed. This indicates potential command and control (C2) communication or data exfiltration by malware attempting to anonymize its network traffic.
Detects possible command execution by a web application or web shell by monitoring `execve` and `execveat` syscalls initiated by the web server's user ID (e.g., euid 33 for www-data). This rule specifically targets Linux systems using auditd for logging, requiring a specific auditd configuration to capture these events.
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