New processes can start on a Linux server for various reasons, some of which might indicate suspicious activity. Here are common reasons or sources for new process creation on a Linux server along with examples:
User Login:
Reason: A user logging into the system can trigger the creation of new processes associated with their session.
Example: When a user logs in via SSH or console, processes such as shell sessions (bash, zsh, etc.) are spawned.
Scheduled Tasks (Cron Jobs):
Reason: Scheduled tasks configured via cron can launch processes at specific times.
Example: A cron job set to run a script or command periodically, such as system maintenance tasks or backups.
Service Start-Up:
Reason: Starting or restarting system services or daemons can lead to the creation of new processes.
Example: Starting the Apache web server (httpd), MySQL database (mysqld), or SSH server (sshd) results in new processes.
Software Installation/Update:
Reason: Installing or updating software packages may involve running installation scripts or daemon processes.
Example: Installing new software via package manager (apt, yum, pacman) or running installer scripts (./install.sh) can spawn new processes.
Malicious Activity:
Reason: Malicious actors gaining unauthorized access to the system can create new processes to perform malicious actions or maintain persistence.
Example: Launching backdoor shells, privilege escalation tools, or malware payloads can result in new processes.
Exploitation:
Reason: Successful exploitation of vulnerabilities in system services or applications can lead to the execution of malicious code, spawning new processes.
Example: Exploiting a vulnerable web server to execute arbitrary commands, leading to the creation of a new process.
Script Execution:
Reason: Execution of scripts, especially those obtained from untrusted sources, can result in the creation of new processes.
Example: Running a malicious shell script (./malicious_script.sh) downloaded from the internet or received via email attachment.
Resource-Intensive Tasks:
Reason: Running resource-intensive tasks such as data processing, compilation, or cryptographic operations can generate new processes.
Example: Compiling software from source code (make), running database queries, or encrypting/decrypting data.
Automatic Updates:
Reason: Automatic updates for software or system components may trigger the execution of update scripts or processes.
Example: Automatically applying security patches or updates via tools like unattended-upgrades can start new processes.
Hardware Events:
Reason: Hardware events such as device insertion or removal can lead to the execution of associated processes.
Example: Plugging in a USB drive may trigger the execution of processes for mounting and accessing the device.
Monitoring and understanding the reasons for new process creation on your Linux server can help differentiate between normal system activities and potentially malicious behavior. It's essential to regularly review process activity and investigate any anomalies to maintain system security.
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