Prerequisites
Windows operating system
Congratulations and
well done to Josh Sokol for winning 2014 Toolsmith Tool of the Year with his
very popular SimpleRisk!
Overview
Sysmon 2.0 was welcomed to the world on 19 JAN 2015,
warranting immediate attention as part of The
State of Cybersecurity focus for February’s ISSA Journal. If you want to
better understand the state of cybersecurity on your Windows systems, consider
System Monitor (Sysmon) a requirement. Sysmon is “a Windows system service and
device driver that, once installed on a system, remains resident across system
reboots to monitor and log system activity to the Windows event log. It
provides detailed information about process creations, network connections, and
changes to file creation time.” The
real upside is that you can ship related events using Windows Event Collection
or the agent provided as part of your preferred SIEM implementation. You can
also conduct simple exports of EVTX files during forensic or malware runtime
analysis for parsing and queries. I built EventViz in R, as a Shiny app, to
simplify this process and read CSV exports from Windows Event Viewer. It’s a
work in progress to be certain, but one you can make immediate use of in order to
pivot on key data in Sysmon logs.
I pinged Thomas Garnier, who along with Microsoft Azure
CTO Mark Russinovich, created Sysmon. Thomas pointed out that the need to
understand our networks, how they are used or abused, has never been higher. He
also reminded us that, unfortunately, there is a gap between the information
needed by network defenders and the information provided by operating systems
across versions. To that end, “Sysinternals
Sysmon was created to provide rich information across OS versions while running
in the background staying resident across reboots. It provides detailed
information on process creation, image loading, driver loading, network
connections and more. It allows you to easily filter generated events and
update its configuration while it is still running. All the activities are
captured in the Windows event log to integrate with existing Windows Event
Collection or SIEM solutions.”
Of the eight Event IDs generated by Sysmon, you can
consider six immediately useful for enhancing situational awareness and
strengthened defenses. You’ll want to tune and optimize how you configure
Sysmon so you don’t flood your logging systems with data you determine later
isn’t as helpful as you hoped. The resulting events can be quite noisy given
the plethora of data made available per the following quick event overview:
·
Event ID
1: Process creation
o The
process creation event provides extended information about a newly created
process.
·
Event ID
2: A process changed a file creation time
o The
change file creation time event is registered when a file creation time is
explicitly modified by a process. Attackers may change the file creation time
of a backdoor to make it look like it was installed with the operating system,
but many processes legitimately change the creation time of a file.
·
Event ID
3: Network connection
o The
network connection event logs TCP/UDP connections on the machine. It is
disabled by default.
·
Event ID
4: Sysmon service state changed
o The
service state change event reports the state of the Sysmon service (started or
stopped).
·
Event ID
5: Process terminated
o The
process terminate event reports when a process terminates.
·
Event ID
6: Driver loaded
o The
driver loaded events provides information about a driver being loaded on the
system.
·
Event ID
7: Image loaded
o The
image loaded event logs when a module is loaded in a specific process. This
event is disabled by default and needs to be configured with the –l option.
I love enabling the monitoring of images loaded during
malware and forensic analysis but as the Sysmon content says, “this event
should be configured carefully, as monitoring all image load events will
generate a large number of events.” I’ll show you these Event IDs come to play
during review of a system compromised by a Trojan:Win32/Beaugrit.gen!AAA sample
using EventViz to analyze Sysmon logs. Beaugrit.gen is a rootkit that makes
outbound connections to request data and download files while also interacting
with Internet Explorer.
Sysmon
installation
I had the best luck downloading Sysmon and unpacking it
into a temp directory. From an
administrator command prompt I changed directory to the temp directory and
first ran Sysmon.exe -accepteula –i.
This accepts the EULA, installs Sysmon as a service, and drops Sysmon.exe in C:\Windows, making it available at any command prompt path. I
exited the first administrator command prompt, spawned another one, and ran sysmon –m. This step installs the event manifest, which
helps you avoid verbose and erroneous log messages such as “The description for
Event ID 5 from source Microsoft-Windows-Sysmon cannot be found.” I followed
that with sysmon -c -n -l -h
md5,sha1,sha256. The -c flag
updates the existing configuration, -n
enables logging of network connections (Event ID 3), -l enables logging the loading (can be noisy) of modules (Event ID
7), and -h defines what hashes you
wish to collect as part of event messaging. You may be happier with just one
hash type configured to again reduce volume. Once installed and properly
configured you’ll find Sysmon logs in the Event Viewer under Applications and
Services Logs | Microsoft | Windows | Sysmon | Operational as seen in Figure 1.
 |
| Figure 1 – Sysmon Operational log entries in Event Viewer |
Analysis with EventViz
Collecting logs is one thing
but making quick use of them is the real trick. There are so many ways and
means with which to review and respond to particular events as defined by
detection and rules logic. Piping Sysmon logs to your collection mechanism is
highly recommended. Windows Event Collection/Windows Event Forwarding are
incredibly useful, the results of which can be consumed by numerous commercial
products. Additionally there are free and open source frameworks that you can
leverage. Enterprise Log Search and Archive (ELSA)
immediately comes to mind as does the ELK stack (Elasticsearch, Logstash,
Kibana). See Josh Lewis’ Advanced ThreatDetection with Sysmon, WEF and Elasticsearch (AKA Panther Detect) as a
great reference and pointer.
There are also excellent uses
for Sysmon that don’t require enterprise collection methods. You may have
single instances of dedicated or virtual hosts that are utilized for runtime
analysis of malware and/or other malfeasance. I utilized just such a Windows 7
SP1 virtual machine to test Sysmon capabilities with the above mentioned Beaugrit.gen
sample. You can of course utilize the built-in Windows Event Viewer but ease of
use and quick pivots and queries are not its strong suit. I’ve started on
EventViz to address this issue and plan to keep developing against it. For
folks with an appreciation for R, this is a nice exemplar for its use. If you
need a good primer on using R for information security-related purposes, I’ve
got you covered there. In January, ADMIN Magazine published my article SecurityData Analytics and Visualization with R, which is a convenient and directly
useful way for you to get your feet wet with R.
Use of EventViz currently
assumes you’ve got a version of R installed, as well as RStudio. At an RStudio
console prompt be sure to run install.packages("shiny")
as EventViz is a Shiny app that requires the Shiny package. Create a directory
where you’d plan to store R scripts, and create an apps directory therein, and an EventViz
directory in the apps directory. Mine
is C:\coding\R\apps\EventViz as an
example. Copy server.R and ui.R, as well as the example CSV file
we’re discussing here, to the EventViz
directory; you can download them from my Github EventViz repository. Open server.R
and ui.R and click Run App as seen in Figure 2.
 |
| Figure 2 - Run the EventViz Shiny app |
Give it a few minutes it may
take a bit to load as it is a crowded log set given the verbosity of Event ID 7
(Image loaded), again, enable it with caution. I’m working on EventViz
performance with larger files but you’ll see how Event ID 7 helps us here
though. Once it’s loaded you’ll have Figure 3 in a Shiny window. You also have
the option to open it in a browser.
 |
| Figure 3 - EventViz UI |
Each of the drop-down menus
represents a column heading in the sysmon.csv albeit with a little manipulation
via R where I renamed them and added a header for the messages column.
I’ll work with a bit of
insider knowledge given my familiarity with the malware sample but as long as
you have a potential indicator of compromise (IOC) such as an IP address or
malicious executable name you can get started. I knew that the sample phones
home to 920zl.com. When I conducted a lookup on this domain (malicious) it
returned an IP address of 124.207.29.185 in Beijing. You may now imagine my
shocked face. Let’s start our results analysis and visualization with that IP
address. I copied it to the EventViz search field and it quickly filter two
results from 9270 entries as seen in Figure 4. This filter is much faster than
the initial app load as the whole data set is now immediately available in
memory. This is both a benefit and a curse with R. It’s performant once loaded
but a memory hog thereafter and it’s not well known for cleaning up after
itself.
 |
| Figure 4 - EventViz IP address search results |
Sysmon Event ID 3 which logs
detected network connections trapped C:\tmp\server.exe
making a connection to our suspect IP address. Nice, now we have a new pivot
options. You could use the Event ID drop-down to filter for all Event ID 3’s
for all network connections. I chose to filter Sysmon Event ID 7 and searched server.exe. The results directly matched
Virus Total behavioral information for this sample, specifically the runtime
DLLs. Sysmon’s Event ID 7 ImageLoad logic clearly shows server.exe acting as indicated by VirusTotal per Figure 5.
 |
| Figure 5 – EventID 7 ImageLoad matches VirusTotal |
Drill in via Event ID 1
ProcessCreate and you’ll find that server.exe
was spawned by explorer.exe. The
victim (me) clicked it (derp). There are endless filter and pivot options given
the data provided by Sysmon and quick filter capabilities in EventViz. Eventually
(pun intended), EventViz will allow you to also analyze other Windows event log
types such as the Security log.
In Conclusion
Sysmon clearly goes above and beyond default Window event
logging by offering insightful and detailed event data. Coupled with collection
and SIEM deployments, Sysmon can be an incredible weapon as part of your
detection logic. Marry your queries up with specific threat indicators and you
may be both pleased and horrified (in a good way) with the results. Watch the
TechNet blog and the Sysinternals site for further updates to Sysmon. For quick
reviews during runtime analysis or dirty forensics a viewer such as EventViz
might be useful assuming you export to your Sysmon EVTX file to CSV. Keep an
eye on the Github site for improvements and updates. I plan to add a file
selector so you can choose from a directory of CSV files. For other feature
requests you can submit via Github.
Ping me via email or Twitter if you have questions (russ
at holisticinfosec dot org or @holisticinfosec).
Cheers…until next month.
Thomas Garnier, Sysmon 2.0 developer
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