LSMS – Linux Security And Monitoring Scripts

Linux Security and Monitoring Scripts. These are a collection of security and monitoring scripts you can use to monitor your Linux installation for security-related events or for an investigation. Each script works on its own and is independent of other scripts. The scripts can be set up to either print out their results, send them to you via mail, or using AlertR as notification channel.

Repository Structure

The scripts are located in the directory scripts/. Each script contains a short summary in the header of the file with a description of what it is supposed to do, (if needed) dependencies that have to be installed and (if available) references to where the idea for this script stems from.

Each script has a configuration file in the scripts/config/ directory to configure it. If the configuration file was not found during the execution of the script, the script will fall back to default settings and print out the results. Hence, it is not necessary to provide a configuration file.

The scripts/lib/ directory contains code that is shared between different scripts.

Scripts using a monitor_ prefix hold a state and are only useful for monitoring purposes. A single usage of them for an investigation will only result in showing the current state the Linux system and not changes that might be relevant for the system’s security. If you want to establish the current state of your system as benign for these scripts, you can provide the --init argument.

Usage

Take a look at the header of the script you want to execute. It contains a short description what this script is supposed to do and what requirements are needed (if any needed at all). If requirements are needed, install them before running the script.

The shared configuration file scripts/config/config.py contains settings that are used by all scripts. Furthermore, each script can be configured by using the corresponding configuration file in the scripts/config/ directory. If no configuration file was found, a default setting is used and the results are printed out.

Finally, you can run all configured scripts by executing start_search.py (which is located in the main directory) or by executing each script manually. A Python3 interpreter is needed to run the scripts.

Monitoring

If you want to use the scripts to monitor your Linux system constantly, you have to perform the following steps:

1. Set up a notification channel that is supported by the scripts (currently printing out, mail, or AlertR).

2. Configure the scripts that you want to run using the configuration files in the scripts/config/ directory.

3. Execute start_search.py with the --init argument to initialize the scripts with the monitor_ prefix and let them establish a state of your system. However, this assumes that your system is currently uncompromised. If you are unsure of this, you should verify its current state.

4. Set up a cron job as root user that executes start_search.py (e.g., 0 * * * * root /opt/LSMS/start_search.py to start the search hourly).

List of Scripts

Name	Script
Monitoring cron files	monitor_cron.py
Monitoring /etc/hosts file	monitor_hosts_file.py
Monitoring /etc/ld.so.preload file	monitor_ld_preload.py
Monitoring /etc/passwd file	monitor_passwd.py
Monitoring modules	monitor_modules.py
Monitoring SSH authorized_keys files	monitor_ssh_authorized_keys.py
Monitoring systemd unit files	monitor_systemd_units.py
Search executables in /dev/shm	search_dev_shm.py
Search fileless programs (memfd_create)	search_memfd_create.py
Search hidden ELF files	search_hidden_exe.py
Search immutable files	search_immutable_files.py
Search kernel thread impersonations	search_non_kthreads.py
Search processes that were started by a now disconnected SSH session	search_ssh_leftover_processes.py
Search running deleted programs	search_deleted_exe.py
Test script to check if alerting works	test_alert.py
Verify integrity of installed .deb packages	verify_deb_packages.py