This version is considered safe to deploy in production environments without kext, but still subject to active development with frequent releases.
xnumon is a monitoring agent that produces system activity logs intended to be suitable for monitoring potentially large fleets of macOS systems for malware and intrusions. It aims at providing similar capabilities on macOS that sysmon provides on Windows.
Currently implemented are the following log events:
- xnumon-ops[0] and xnumon-stats[1] for in-band monitoring of agent status and activity metrics.
- image-exec[2]: a process has replaced its executable image as a result of calling one of the execve(2) or posix_spawn(2) family syscalls.
- process-access[3]: a process has accessed and possibly manipulated another process using either the task_for_pid or ptrace(2) syscalls.
- launchd-add[4]: a process has added or modified a launch daemon or launch agent plist. (experimental)
xnumon provides context information such as executable image hashes, code signing meta-data, script shebang handling, and the history of previous executable images that led to the current process state. It does so by tracking fork and other syscalls instead of relying only on the ppid, which can change over the lifetime of a process.
A supported version of OS X or macOS, currently:
- OS X 10.11 El Capitan
- macOS 10.12 Sierra
- macOS 10.13 High Sierra
- macOS 10.14 Mojave
See the xnumon wiki for further documentation. While the wiki is still work in progress, some useful starting points:
cat /var/log/xnumon.log | jq 'select(.eventcode==0)'xnumonctlxnumon -hdmesg | grep xnumon
The installer package published on the
xnumon website
will install the daemon, the control utility and a default configuration which
by default will log to /var/log/xnumon.log in JSON Lines format. It will
also install a matching newsyslog configuration and the optional kernel
extension. The kernel extension is currently unsigned and as such will not be
usable in production environments unless you control a kext signing certificate
(see «Kernel Extension» below).
The extensively commented default configuration is installed to
/Library/Application Support/ch.roe.xnumon/configuration.plist-default.
While the defaults are as sensible as possible, you will most likely want to
maintain a custom configuration at
/Library/Application Support/ch.roe.xnumon/configuration.plist to be used
in favour of the default configuration, especially for enterprise deployments.
In addition to installing xnumon, you will want to make sure that auditd does
not clobber the global kernel audit policy. Make sure the argv policy flag
is enabled in /etc/security/audit_control, which is the default. Right now,
xnumon does not process the additional information provided by the arge flag,
but most likely will start doing so in a future release.
In order to make the logs useful and to get them out of reach of malware and
attackers, it is recommended to continuously forward logs to central log
collection infrastructure. A sample Splunk configuration for ingesting xnumon
logs can be found in extra/splunk.
The xnumon kext is optional and provides reliable acquisition of image hashes and code signing information even for short-living images using the Kauth KPI. The kernel extension is currently unsigned and therefore cannot be deployed unless you own a kernel signing certificate. A kernel signing certificate for xnumon has been requested from Apple, but has not been approved yet.
To load the unsigned kext for testing and development, you need to disable
System Integrity Protection (SIP) for kexts. Reboot to repair mode by pressing
cmd⌘+r during boot and from within the repair console,
run csrutil enable --without kext. This will also turn off the kext user
consent requirement of High Sierra.
In addition to a code signature, the kext needs more field testing, especially compatibility tests with other security solutions, before recommending large-scale deployments.
xnumonctl uninstall
This will remove all traces of this package from your system, including logs
at the default location /var/log/xnumon.log*, but not including the config
at /Library/Application Support/ch.roe.xnumon/configuration.plist unless it
is the same as the default config.
Building an unsigned userland binary and kernel extension requires Xcode command line tools. The userland binary requires only the CoreFoundation and Security frameworks and libbsm; there are no third-party dependencies.
Building a signed userland binary requires an Application Developer ID certificate from Apple.
Building a signed kernel extension requires a Kext Developer ID certificate from Apple.
Building signed binary packages requires pandoc and an Installer Developer ID
certificate from Apple.
Use the metrics in eventcode 1 events to monitor xnumon internals, possibly reducing the interval it gets generated in the configuration.
Enable debug in the configuration and run xnumonctl logstderr to change
the launchd plist for xnumon to send stderr to /var/log/xnumon.stderr.
This will allow you to get context information for fatal events that would
otherwise only be visible in one of the eventcode 1 metrics.
For short-term debugging during development you can also just unload xnumon
using xnumonctl unload and run xnumon with -o debug=true on the command
line.
Pass DEBUG=1 to make in order to build a debug version of xnumon that
includes symbols and optionally has additional debugging code. See make file
for details.
Copyright (c) 2017-2018, Daniel Roethlisberger.
All rights reserved.
Licensed under the Open Software License version 3.0.
Contains components licensed under BSD and MIT licenses.
See LICENSE, LICENSE.contrib and LICENSE.third as well as the respective
source file headers for details.
If you are interested in supporting the development and maintenance of xnumon, contact me.