Sysmon v15.15
By Mark Russinovich and Thomas Garnier
Published: July 23, 2024
Download Sysmon (4.6 MB)
Download Sysmon for Linux (GitHub)
System Monitor (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. By collecting the events it generates using Windows Event Collection or SIEM agents and subsequently analyzing them, you can identify malicious or anomalous activity and understand how intruders and malware operate on your network. The service runs as a protected process, thus disallowing a wide range of user mode interactions.
Note that Sysmon does not provide analysis of the events it generates, nor does it attempt to hide itself from attackers.
Sysmon includes the following capabilities:
- Logs process creation with full command line for both current and parent processes.
- Records the hash of process image files using SHA1 (the default), MD5, SHA256 or IMPHASH.
- Multiple hashes can be used at the same time.
- Includes a process GUID in process create events to allow for correlation of events even when Windows reuses process IDs.
- Includes a session GUID in each event to allow correlation of events on same logon session.
- Logs loading of drivers or DLLs with their signatures and hashes.
- Logs opens for raw read access of disks and volumes.
- Optionally logs network connections, including each connection’s source process, IP addresses, port numbers, hostnames and port names.
- Detects changes in file creation time to understand when a file was really created. Modification of file create timestamps is a technique commonly used by malware to cover its tracks.
- Automatically reload configuration if changed in the registry.
- Rule filtering to include or exclude certain events dynamically.
- Generates events from early in the boot process to capture activity made by even sophisticated kernel-mode malware.
Common usage featuring simple command-line options to install and uninstall Sysmon, as well as to check and modify its configuration:
Install: sysmon64 -i [<configfile>]
Update configuration: sysmon64 -c [<configfile>]
Install event manifest: sysmon64 -m
Print schema: sysmon64 -s
Uninstall: sysmon64 -u [force]
Parameter | Description |
---|---|
-i | Install service and driver. Optionally take a configuration file. |
-c | Update configuration of an installed Sysmon driver or dump the current configuration if no other argument is provided. Optionally takes a configuration file. |
-m | Install the event manifest (implicitly done on service install as well). |
-s | Print configuration schema definition. |
-u | Uninstall service and driver. Using -u force causes uninstall to proceed even when some components are not installed. |
The service logs events immediately and the driver installs as a boot-start driver to capture activity from early in the boot that the service will write to the event log when it starts.
On Vista and higher, events are stored in
Applications and Services Logs/Microsoft/Windows/Sysmon/Operational
.
On older systems, events are written to the System
event log.
If you need more information on configuration files, use the -? config
command.
Specify -accepteula
to automatically accept the EULA on installation,
otherwise you will be interactively prompted to accept it.
Neither install nor uninstall requires a reboot.
Install with default settings (process images hashed with SHA1 and no network monitoring)
sysmon -accepteula -i
Install Sysmon with a configuration file (as described below)
sysmon -accepteula -i c:\windows\config.xml
Uninstall
sysmon -u
Dump the current configuration
sysmon -c
Reconfigure an active Sysmon with a configuration file (as described below)
sysmon -c c:\windows\config.xml
Change the configuration to default settings
sysmon -c --
Show the configuration schema
sysmon -s
On Vista and higher, events are stored in
Applications and Services Logs/Microsoft/Windows/Sysmon/Operational
, and on
older systems events are written to the System
event log.
Event timestamps are in UTC standard time.
The following are examples of each event type that Sysmon generates.
The process creation event provides extended information about a newly
created process. The full command line provides context on the process
execution. The ProcessGUID
field is a unique value for this process
across a domain to make event correlation easier. The hash is a full
hash of the file with the algorithms in the HashType
field.
The change file creation time event is registered when a file creation time is explicitly modified by a process. This event helps tracking the real creation time of a file. Attackers may change the file creation time of a backdoor to make it look like it was installed with the operating system. Note that many processes legitimately change the creation time of a file; it does not necessarily indicate malicious activity.
The network connection event logs TCP/UDP connections on the machine. It
is disabled by default. Each connection is linked to a process through
the ProcessId
and ProcessGuid
fields. The event also contains the source
and destination host names IP addresses, port numbers and IPv6 status.
The service state change event reports the state of the Sysmon service (started or stopped).
The process terminate event reports when a process terminates. It
provides the UtcTime
, ProcessGuid
and ProcessId
of the process.
The driver loaded events provides information about a driver being loaded on the system. The configured hashes are provided as well as signature information. The signature is created asynchronously for performance reasons and indicates if the file was removed after loading.
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. It indicates the process in which the module is
loaded, hashes and signature information. The signature is created
asynchronously for performance reasons and indicates if the file was
removed after loading. This event should be configured carefully, as
monitoring all image load events will generate a significant amount of logging.
The CreateRemoteThread
event detects when a process creates a thread in
another process. This technique is used by malware to inject code and
hide in other processes. The event indicates the source and target
process. It gives information on the code that will be run in the new
thread: StartAddress
, StartModule
and StartFunction
. Note that
StartModule
and StartFunction
fields are inferred, they might be empty
if the starting address is outside loaded modules or known exported
functions.
The RawAccessRead
event detects when a process conducts reading
operations from the drive using the \\.\
denotation. This technique
is often used by malware for data exfiltration of files that are locked
for reading, as well as to avoid file access auditing tools. The event
indicates the source process and target device.
The process accessed event reports when a process opens another process, an operation that’s often followed by information queries or reading and writing the address space of the target process. This enables detection of hacking tools that read the memory contents of processes like Local Security Authority (Lsass.exe) in order to steal credentials for use in Pass-the-Hash attacks. Enabling it can generate significant amounts of logging if there are diagnostic utilities active that repeatedly open processes to query their state, so it generally should only be done so with filters that remove expected accesses.
File create operations are logged when a file is created or overwritten. This event is useful for monitoring autostart locations, like the Startup folder, as well as temporary and download directories, which are common places malware drops during initial infection.
Registry key and value create and delete operations map to this event type, which can be useful for monitoring for changes to Registry autostart locations, or specific malware registry modifications.
Sysmon uses abbreviated versions of Registry root key names, with the following mappings:
Key name | Abbreviation |
---|---|
HKEY_LOCAL_MACHINE |
HKLM |
HKEY_USERS |
HKU |
HKEY_LOCAL_MACHINE\System\ControlSet00x |
HKLM\System\CurrentControlSet |
HKEY_LOCAL_MACHINE\Classes |
HKCR |
This Registry event type identifies Registry value modifications. The
event records the value written for Registry values of type DWORD
and
QWORD
.
Registry key and value rename operations map to this event type, recording the new name of the key or value that was renamed.
This event logs when a named file stream is created, and it generates
events that log the hash of the contents of the file to which the stream
is assigned (the unnamed stream), as well as the contents of the named
stream. There are malware variants that drop their executables or
configuration settings via browser downloads, and this event is aimed at
capturing that based on the browser attaching a Zone.Identifier
"mark of
the web" stream.
This event logs changes in the Sysmon configuration - for example when the filtering rules are updated.
This event generates when a named pipe is created. Malware often uses named pipes for interprocess communication.
This event logs when a named pipe connection is made between a client and a server.
When a WMI event filter is registered, which is a method used by malware to execute, this event logs the WMI namespace, filter name and filter expression.
This event logs the registration of WMI consumers, recording the consumer name, log, and destination.
When a consumer binds to a filter, this event logs the consumer name and filter path.
This event is generated when a process executes a DNS query, whether the result is successful or fails, cached or not. The telemetry for this event was added for Windows 8.1 so it is not available on Windows 7 and earlier.
A file was deleted. Additionally to logging the event, the deleted file is also
saved in the ArchiveDirectory
(which is C:\Sysmon
by default). Under normal
operating conditions this directory might grow to an unreasonable size - see
event ID 26: FileDeleteDetected
for similar behavior but without saving the
deleted files.
This event is generated when the system clipboard contents change.
This event is generated when process hiding techniques such as "hollow" or "herpaderp" are being detected.
A file was deleted.
This event is generated when Sysmon detects and blocks the creation of executable files (PE format).
This event is generated when Sysmon detects and blocks file shredding from tools such as SDelete.
This event is generated when Sysmon detects the creation of a new executable file (PE format).
This event is generated when an error occurred within Sysmon. They can happen if the system is under heavy load and certain tasks could not be performed or a bug exists in the Sysmon service, or even if certain security and integrity conditions are not met. You can report any bugs on the Sysinternals forum or over Twitter (@markrussinovich).
Configuration files can be specified after the -i (installation) or -c (installation) configuration switches. They make it easier to deploy a preset configuration and to filter captured events.
A simple configuration xml file looks like this:
<Sysmon schemaversion="4.82">
<!-- Capture all hashes -->
<HashAlgorithms>*</HashAlgorithms>
<EventFiltering>
<!-- Log all drivers except if the signature -->
<!-- contains Microsoft or Windows -->
<DriverLoad onmatch="exclude">
<Signature condition="contains">microsoft</Signature>
<Signature condition="contains">windows</Signature>
</DriverLoad>
<!-- Do not log process termination -->
<ProcessTerminate onmatch="include" />
<!-- Log network connection if the destination port equal 443 -->
<!-- or 80, and process isn't InternetExplorer -->
<NetworkConnect onmatch="include">
<DestinationPort>443</DestinationPort>
<DestinationPort>80</DestinationPort>
</NetworkConnect>
<NetworkConnect onmatch="exclude">
<Image condition="end with">iexplore.exe</Image>
</NetworkConnect>
</EventFiltering>
</Sysmon>
The configuration file contains a schemaversion attribute on the Sysmon
tag. This version is independent from the Sysmon binary version and
allows the parsing of older configuration files. You can get the current
schema version by using the "-? config
" command line. Configuration
entries are directly under the Sysmon
tag and filters are under the
EventFiltering
tag.
Configuration entries are similar to command line switches and include the following
Configuration entries include the following:
Entry | Value | Description |
---|---|---|
ArchiveDirectory | String | Name of directories at volume roots into which copy-on-delete files are moved. The directory is protected with a System ACL (you can use PsExec from Sysinternals to access the directory using psexec -sid cmd ). Default: Sysmon |
CheckRevocation | Boolean | Controls signature revocation checks. Default: True |
CopyOnDeletePE | Boolean | Preserves deleted executable image files. Default: False |
CopyOnDeleteSIDs | Strings | Comma-separated list of account SIDs for which file deletes will be preserved. |
CopyOnDeleteExtensions | Strings | Extensions for files that are preserved on delete. |
CopyOnDeleteProcesses | Strings | Process name(s) for which file deletes will be preserved. |
DnsLookup | Boolean | Controls reverse DNS lookup. Default: True |
DriverName | String | Uses specified name for driver and service images. |
HashAlgorithms | Strings | Hash algorithm(s) to apply for hashing. Algorithms supported include MD5, SHA1, SHA256, IMPHASH and * (all). Default: None |
Command line switches have their configuration entry described in the Sysmon usage
output. Parameters are optional based on the tag. If a command line
switch also enables an event, it needs to be configured though its
filter tag. You can specify the -s
switch to have Sysmon print the full
configuration schema, including event tags as well as the field names
and types for each event. For example, here’s the schema for the
RawAccessRead
event type:
<event name="SYSMON_RAWACCESS_READ" value="9" level="Informational "template="RawAccessRead detected" rulename="RawAccessRead" version="2">
<data name="UtcTime" inType="win:UnicodeString" outType="xs:string"/>
<data name="ProcessGuid" inType="win:GUID"/>
<data name="ProcessId" inType="win:UInt32" outType="win:PID"/>
<data name="Image" inType="win:UnicodeString" outType="xs:string"/>
<data name="Device" inType="win:UnicodeString" outType="xs:string"/>
</event>
Event filtering allows you to filter generated events. In many cases events can be noisy and gathering everything is not possible. For example, you might be interested in network connections only for a certain process, but not all of them. You can filter the output on the host reducing the data to collect.
Each event has its own filter tag under the EventFiltering node in a configuration file:
ID | Tag | Event |
---|---|---|
1 | ProcessCreate | Process Create |
2 | FileCreateTime | File creation time |
3 | NetworkConnect | Network connection detected |
4 | n/a | Sysmon service state change (cannot be filtered) |
5 | ProcessTerminate | Process terminated |
6 | DriverLoad | Driver Loaded |
7 | ImageLoad | Image loaded |
8 | CreateRemoteThread | CreateRemoteThread detected |
9 | RawAccessRead | RawAccessRead detected |
10 | ProcessAccess | Process accessed |
11 | FileCreate | File created |
12 | RegistryEvent | Registry object added or deleted |
13 | RegistryEvent | Registry value set |
14 | RegistryEvent | Registry object renamed |
15 | FileCreateStreamHash | File stream created |
16 | n/a | Sysmon configuration change (cannot be filtered) |
17 | PipeEvent | Named pipe created |
18 | PipeEvent | Named pipe connected |
19 | WmiEvent | WMI filter |
20 | WmiEvent | WMI consumer |
21 | WmiEvent | WMI consumer filter |
22 | DNSQuery | DNS query |
23 | FileDelete | File Delete archived |
24 | ClipboardChange | New content in the clipboard |
25 | ProcessTampering | Process image change |
26 | FileDeleteDetected | File Delete logged |
27 | FileBlockExecutable | File Block Executable |
28 | FileBlockShredding | File Block Shredding |
29 | FileExecutableDetected | File Executable Detected |
You can also find these tags in the event viewer on the task name.
The onmatch
filter is applied if events are matched. It can be changed
with the onmatch
attribute for the filter tag. If the value is
"include"
, it means only matched events are included. If it is set to
"exclude"
, the event will be included except if a rule match. You can
specify both an include filter set and an exclude filter set for each
event ID, where exclude matches take precedence.
Each filter can include zero or more rules. Each tag under the filter tag is a field name from the event. Rules that specify a condition for the same field name behave as OR conditions, and ones that specify different field name behave as AND conditions. Field rules can also use conditions to match a value. The conditions are as follows (all are case insensitive):
Condition | Description |
---|---|
is | Default, values are equals |
is any | The field is one of the ; delimited values |
is not | Values are different |
contains | The field contains this value |
contains any | The field contains any of the ; delimited values |
contains all | The field contains all of the ; delimited values |
excludes | The field does not contain this value |
excludes any | The field does not contain one or more of the ; delimited values |
excludes all | The field does not contain any of the ; delimited values |
begin with | The field begins with this value |
end with | The field ends with this value |
not begin with | The field does not begin with this value |
not end with | The field does not end with this value |
less than | Lexicographical comparison is less than zero |
more than | Lexicographical comparison is more than zero |
image | Match an image path (full path or only image name). For example: lsass.exe will match c:\windows\system32\lsass.exe |
You can use a different condition by specifying it as an attribute. This excludes network activity from processes with iexplore.exe in their path:
<NetworkConnect onmatch="exclude">
<Image condition="contains">iexplore.exe</Image>
</NetworkConnect>
To have Sysmon report which rule match resulted in an event being logged, add names to rules:
<NetworkConnect onmatch="exclude">
<Image name="network iexplore" condition="contains">iexplore.exe</Image>
</NetworkConnect>
You can use both include and exclude rules for the same tag, where exclude rules override include rules. Within a rule, filter conditions have OR behavior.
In the sample configuration shown earlier, the networking filter uses both an
include and exclude rule to capture activity to port 80 and 443 by all processes
except those that have iexplore.exe
in their name.
It is also possible to override the way that rules are combined by using a rule group which allows the rule combine type for one or more events to be set explicitly to AND or OR.
The following example demonstrates this usage. In the first rule group, a
process create event will be generated when timeout.exe
is executed only with
a command line argument of 100
, but a process terminate event will be
generated for the termination of ping.exe
and timeout.exe
.
<EventFiltering>
<RuleGroup name="group 1" groupRelation="and">
<ProcessCreate onmatch="include">
<Image condition="contains">timeout.exe</Image>
<CommandLine condition="contains">100</CommandLine>
</ProcessCreate>
</RuleGroup>
<RuleGroup groupRelation="or">
<ProcessTerminate onmatch="include">
<Image condition="contains">timeout.exe</Image>
<Image condition="contains">ping.exe</Image>
</ProcessTerminate>
</RuleGroup>
<ImageLoad onmatch="include"/>
</EventFiltering>
Download Sysmon (4.6 MB)
Runs on:
- Client: Windows 10 and higher.
- Server: Windows Server 2016 and higher.