Event Log Archives - Page 2 of 7

From PowerShell to P0W3rH3LL – Auditing PowerShell

January 29, 2018June 9, 2022 ingmar.koecher 0 Comment Event Log, EventSentry, Monitoring, Security, Tools & Utilities powershell, powershell attack, powershell attack scripts, powershell auditing, powershell hacking, powershell security, powershell security policy

Imagine someone getting the seemingly innocent ability to run a couple of commands on a machine on your network WITHOUT installing any new software, but those commands resulting in a reverse shell running on that same machine – giving the intruder a convenient outpost in your network. Now stretch your imagination even further and pretend that all of this happens without leaving any unusual traces in logs – leaving you completely in the dark. It’s like somebody living in your house or apartment yet you have no idea they’re there. Are you getting goose bumps yet?

Not too long ago I talked with Michael, the creator of the popular cheat sheets which cover PowerShell, the Windows Registry, Windows Logging, and more. Michael ran a few scenarios by me that involved exploiting PowerShell and was curious how EventSentry could help detect those. This really sparked my interest in the topic, and after coming up with a few RegEx expressions that could be used in an EventSentry filter I decided to look more into this subject. I really have to take the opportunity to thank Michael here, whose cheat sheets and input helped me come up with this article and the new PowerShell Security event log package in EventSentry.

If you’re not an InfoSec professional then you may not be fully aware that PowerShell – you know, the language you’re supposed to be fluent in by now – is quite commonly used in attacks. In fact, InfoSec already reported back in 2016 that 38% of all attacks utilize PowerShell in one way or another. And let’s be honest – why wouldn’t you utilize a tool that is pretty much guaranteed to be installed while giving you full access to the .NET Framework and all Windows APIs? So if you haven’t already done so, then securing PowerShell in your environment is something you should think about sooner rather than later. This and the follow-up articles will assist you with this effort.

So what’s so potentially bad about PowerShell in particular? Now, Windows has always shipped with VBScript, a scripting language that’s easy to use for both simple and potentially more complex tasks. In fact, most of the things people do in PowerShell can be done with VBScript just the same. A key benefit of PowerShell, however, is the ability to utilize the .NET framework, something VBScript can’t since it can only interact with COM objects. And since PowerShell is, well, a shell, you get to pipe input/output and create powerful one-liners. On top of that, PowerShell contains some nifty features like encoding scripts, making it possible to run fairly complex code without ever having to use an actual .ps1 script file on disk. It’s VBScript on Steroids.

Here are some concrete examples as to what evildoers can do with PowerShell:

- Reverse Shell
- Download malicious payload and execute
- Mimikatz
- UAC Bypass
- Embed PowerShell scripts in images
- Bypass UAC and quietly run scripts elevated
- Write a complete RansomWare implementation in PowerShell
- Fileless attacks
- and boatloads more

Here is a list of sites hosting “aggressive” PowerShell code and frameworks:

PowerShell Versions

Remember when I talked about “without leaving a trace” above? That’s because Microsoft didn’t introduce the ability to log detailed PowerShell activity until version 5, although PowerShell 3 & 4 generate reasonably useful audit logs as well. In order to protect ourselves against PowerShell attacks, we need to first detect it, which we can only do if PowerShell leaves traces. PowerShell’s ability to produce useful audit logs greatly depends on the version, however, which the table below illustrates:

Which version of Windows ships with which version of PowerShell
What is the highest supported version of PowerShell for each version of Windows

For more information on version differences also see Differences between PowerShell versions.

Default PowerShell Version on Windows
PowerShell Version	Release Year	Windows Version	Prerequisites
1.0	2006	Windows Server 2008	None
2.0	2009	Windows 7 Windows Server 2008 R2	Microsoft .NET Framework 2.0.50727
3.0	2012	Windows 8 Windows Server 2012	Microsoft .NET Framework 4
4.0	2013	Windows 8.1 Windows Server 2012 R2	Microsoft .NET Framework 4.5
5.1	2017	Windows 10	Microsoft .NET Framework 4.5.2
5.1	2017	Windows Server 2016	Microsoft .NET Framework 4.5.2 (already installed in 2012 and later)
5.1	2017	Windows Server 2019	Microsoft .NET Framework 4.5.2 (already installed in 2012 and later)
All versions of Windows since Server 2008 and the version of PowerShell that it included by default

Default PowerShell vs Highest Supported PowerShell Versions
Windows Version	PowerShell Version Included With Windows	Highest Supported PowerShell Version
Windows Vista (SP2)	2.0	2.0
Windows Server 2008 (SP2)	2.0	3.0
Windows 7 (SP1)	2.0	5.1 / 7.0 Core
Windows Server 2008 R2 (SP1)	5.1	5.1 / 7.0 Core
Windows 8	3.0	5.1 / 7.0 Core
Windows Server 2012	3.0	5.1 / 7.0 Core
Windows 8.1	4.0	5.1 / 7.0 Core
Windows Server 2012 R2	4.0	5.1 / 7.0 Core
Windows 10	5.1	5.1 / 7.0 Core
Windows Server 2016	5.1	5.1 / 7.0 Core
Windows Server 2019	5.1	5.1 / 7.0 Core
Shows the versions of PowerShell that ship with Windows as well as the highest supported version of PowerShell

As you can see from the table above, thankfully most versions of Windows are compatible with PS v5, so unless you’re unfortunate enough to be running Server 2008 (or Vista), you should be able to deploy PowerShell 5.1 to most of your systems. I say most, because some Microsoft applications (e.g. Exchange Server 2010) aren’t compatible with PowerShell v5, so you’ll want to make sure you do some research on those machines that actively use PowerShell to prevent disruption.

Coexistence & Legacy

An important thing to note here is that PowerShell v1/v2 can peacefully coexist with PowerShell v3-v5, while versions 3 and later are always upgraded to the latest version. This means that you could have v2 and v4 installed (and many systems do), but not v3 and v5. What’s also interesting is that PS v2 is installed with every major version of Windows (including Server 2016!) although not usable until the .NET Framework v2.0.50727 is installed.

Starting with EventSentry v3.4.1.34 you can thankfully use EventSentry’s software inventory to determine which versions of PowerShell are installed on your network. If you haven’t manually deployed PS v5 yet and aren’t running Windows Server 2016 widely yet, then you will probably see PowerShell v2 and v4 installed on most hosts on your network. EventSentry’s grouping mechanism comes in real handy here.

PowerShell Version Inventory (click for animation)

Please note that even though PowerShell v2 may be installed on a machine it doesn’t necessarily mean that PowerShell v2 is actually usable. PowerShell relies on the .NET Framework being installed, and PowerShell v2 specifically relies on the .NET Framework 2.0.50727 (which is part of the 3.5 .NET Framework) – something that is usually not installed by default. I will explain later why this is a good thing.

OK, but enough about boring PowerShell versions. If you just remember one thing from the above tables and paragraphs it’s this:

PowerShell v2: Ever prevalent & Bad!
PowerShell v3, v4: Meh.
PowerShell v5.1: Good!

Native PowerShell Event Logging

Since PowerShell v1.0 was first introduced with Windows XP – before the Application & Services logs were available – PowerShell likes to log to two different event logs – both of which you should monitor:

Windows PowerShell
Microsoft-Windows-PowerShell/Operational

Thankfully you don’t need version 5.x to get useful logging – even PowerShell v3 & v4 can log relevant details in the (Windows PowerShell) event log, e.g. the PowerShell command line or commands executed within the PowerShell shell. In fact, even the (decoded) commands are logged to the event log when obfuscated with the -encoded switch.

Logging Options

Logging can be enabled either through group policy or via registry settings. There are three general areas for logging available:

Module Logging
Script Block Logging
PowerShell Transcription

Module Logging
Since everything that is executed in PowerShell is essentially located in a module, module logging will at least generate a high-level audit trail of PowerShell activity and potentially malicious activity. At minimum this will show which commands were executed through PowerShell. This logging level should always be enabled and is useful starting with PS version 3.

Important: Module Logging only works if you specify at least one module to be monitored. Since it’s difficult and cumbersome to predict and edit a list of all modules that could potentially cause harm, I recommend just specifying the * wildcard characters as the module list – see screenshots below.

Script Block Logging
Script Block Logging is more verbose than module logging and provides additional context and output, especially when functions are called and function output itself is invoked as a command. The amount of noise heavily depends on the type of PowerShell activity, but I’d recommend turning this option on as well. If it ends up producing too much noise / volume it can always be disabled or customized later.

Transcription
This provides a full log of all input and output and requires additional considerations in regards to where the transcription files are placed. I’d only recommend this for high-secure environments, you can learn more about it here. Transcript files are stored in the file system, so it’s a little more work than just adding up a couple of registry values. If you enable this feature then you’ll need to make sure that the actual transcript files (which likely contain sensitive data) are protected from unauthorized access.

Enabling Logging

It’s definitely recommended to configure these options via Group Policy to ensure that all machines in the domain receive the settings. If changing group policy is not an option in the short term then you can at least set the registry options until you have an opportunity to set it via group policy. You can use a tool like the EventSentry Admin Assistant to push registry settings out to multiple hosts with just a few clicks.

Group Policy: Configuring this is unfortunately less straightforward than you’d think or expect, depending on the OS version of your domain controller. You can expect the “Module Logging” option to be available in the group policy editor on 2008 R2 and later, however “Script Block Logging” is only available on server 2016 or after manually updating ADMX files. See this thread on how to update your ADMX files. In my environment I just had to replace the PowerShellExecutionPolicy.admx and en-US\PowerShellExecutionPolicy.adml files in the %SYSTEMROOT%\SYSVOL\sysvol\[DOMAINNAME]\Policies\PolicyDefinitions directory with the newer versions after installing the latest version from here.

PowerShell auditing with Group Policy: **Administrative Templates → Windows Components → Windows PowerShell**

Registry: Only the HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\PowerShell key exists by default, the other two sub keys “ModuleLogging” and “ScriptBlockLogging” have to be created before you can add the “EnableModuleLogging” and “EnableScriptblockLogging” DWORD values inside those sub keys.

For Module Logging, as shown in the screenshot below, you’ll also need to create the “ModuleNames” sub key along with a list of modules that will be monitored. I recommend just using the asterisk character which monitors any module.

Configuring PowerShell Event Logging
	Registry	Group Policy
Module Logging	Key: HKLM\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ModuleLogging Name: EnableModuleLogging Data: 1 (DWORD)Key: HKLM\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ModuleLogging\ModuleNames Name: [ModulePattern] Data: [ModulePattern] (REG_SZ)See the screenshot above for example on module logging.	Policies\Administrative Templates\Windows Components\Windows PowerShell\Turn on Module Logging
Script Block Logging	Key: HKLM\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ScriptBlockLogging Name: EnableScriptBlockLogging Data: 1 (DWORD)	Policies\Administrative Templates\Windows Components\Windows PowerShell\Script Block Logging
HKLM = HKEY_LOCAL_MACHINE

You don’t need to restart after setting the registry values, they will become effective immediately. The same applies to group policy – as soon as the target host has applied the group policy settings, PowerShell will enforce the new logging options.

PowerShell logs a lot of different events to two different event logs, and the table below shows the events I have observed on test systems. Even though the table may not be 100% complete, it does list all the events that are relevant for threat detection. If an event is not listed below then it is likely not relevant for forensics. We will update the list if necessary.

Event Log: Windows PowerShell
Event ID	v2	v3	v4	v5	Correlate	Auditing	Notes
400	X	X	X	X	403	Always logged, regardless of logging settings	This even can be used to identify (and terminate) outdated versions of PowerShell running.
403	X	X	X	X	400	Always logged, regardless of logging settings
500	X	X	X	X	501	Requires $LogCommandLifeCycleEvent = $true in profile.ps1	This event is largely useless since it can be bypassed with the -nop command line switch
501	X	X	X	X	500	Requires $LogCommandLifeCycleEvent = $true in profile.ps1	This event is largely useless since it can be bypassed with the -nop command line switch
600	X	X	X	X	500	Always logged, regardless of logging settings
800		X	X	X	500	ModuleLogging	This event is inconsistently logged with PowerShell V3

Event Log: Microsoft-Windows-PowerShell/Operational
Event ID	v2	v3	v4	v5	Correlate	Auditing	Notes
4100				X			Logged when PowerShell encounters an error
4103			X	X		ModuleLogging	May be logged along with 500 & 501
4104				X		ScriptBlockLogging
40961		X	X	X		Always logged, regardless of logging settings
40962		X	X	X		Always logged, regardless of logging settings

What’s interesting to note is that newer versions of PowerShell will often log to both event logs simultaneously.

Security Event Log Auditing

PowerShell logging is great, but given the discrepancies between the different versions and the possibility to evade it (more on that later), I prefer to have as many methods as possible at my disposal that tell me what PowerShell is doing.

Since PowerShell code is usually invoked via powershell.exe (I’m point this out because you technically don’t have to use powershell.exe, and attackers are coming up with creative ways to launch it through other ways – more in part 2 of this series), and because we’re after that processes’ command line, it’s important to monitor Process Start (event id 4688) events from the security event log in addition to events logged by PowerShell itself. This means you’ll need audit the following sub categories from the Detailed Tracking category:

Process Creation: Success and Failure (event id 4688)
Process Termination: Success and Failure (event id 4689)

If you are not using EventSentry then I recommend collecting both 4688 and 4689 events so that you can not only determine whether a powershell.exe process was started, but also how long it remained active. If you are an EventSentry user then you just need to verify that Process Tracking (an object for Compliance Tracking) is enabled and configured to capture the command line of a process. EventSentry can automatically parse and correlate 4688 and 4689 events and provide a history of all processes on a monitored system.

EventSentry users can also utilize the Audit Policy Status page to verify that process creations are indeed being audited. You’ll also want to make sure that “Include command line in process creation events” is activated, so that Windows logs the command line of every process as part of 4688 events. After all it doesn’t help us that much just knowing that powershell.exe has been running, we need to know what exactly it has been running.

This can either be enabled via group policy (Administrative Templates\System\Audit Process Creation\Include command line in process creation events) or via the registry (set HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System\Audit\ProcessCreationIncludeCmdLine_Enabled to 1).

Disclaimer: This option is available starting with Windows 7 / Server 2008 R2, earlier versions of Windows don’t support it. Things are a little easier for EventSentry users, which attempts to obtain the command line of a process if it’s not included in the 4688 event and subsequently makes it available as variable $STR9. But more on that in part 2 when we discuss ways to detect and mitigate attacks.

I hope I was able to convince you of the risks that PowerShell poses, what versions of PowerShell are out there, and what type of logging needs to be enabled in order to detect and stop malicious PowerShell in its tracks. In part 2 I’ll talk about how to actually mitigate PowerShell-based attacks – with specific instructions for EventSentry.

Mr. Robot, Mimikatz and Lateral Movement

December 21, 2017December 22, 2017 ingmar.koecher 0 Comment Event Log, EventSentry, Monitoring, Security, Tips & Tricks, Tools & Utilities lateral movement, mrrobot, real time log monitoring, whoismrrobot

In Mr. Robot‘s episode 9 of season 2 (13:53), Angela Moss needs to obtain the Windows domain password of her superior, Joseph Green, in order to download sensitive documents that would potentially incriminate EvilCorp. Since her attack requires physical access to his computer, she starts with a good old-fashioned social engineering attack to get the only currently present employee in the office to leave.

Once in his office, she uses a USB Rubber Ducky, a fast and automated keyboard emulator, to obtain Joseph’s clear text password using mimikatz. Please note that there are some holes in this scene which I will get into later. For now we’ll assume that she was able to obtain his credentials by having physical access to his computer.

After she gets back to her workstation, she analyzes the capture which reveals Joseph’s password: holidayarmadillo. Not the best password, but for this particular attack the quality of the password wouldn’t have mattered anyways. Mimikatz was (is) able to get the password from memory without utilizing brute force or dictionary techniques. Once she has the password, she logs off and logs back on with Joseph’s user and downloads the documents she needs.

As somebody who helps our users improve the security of their networks, I of course immediately contemplated how this attack could have been detected with EventSentry. Since most users only log on to one workstation on any given day with their user account, Angela logging in with Joseph’s account (resulting in “joseph.green” logging on to two different workstations) would actually be an easy thing to detect.

Introduced with v3.4, collector-side thresholds allow the real-time detection of pretty much any user activity that originates from an event, for example user logons or process launches. You can tell EventSentry that (physical) logons for any user on more than one host (within a given time period – say 9 hours) should trigger an alert (aka as “lateral movement”). Had this been in place at EvilCorp, Angela logging in as Joseph would have immediately triggered an alert. With the right procedures in place, countermeasures could have been taken. Of course most viewers wouldn’t want Angela to be caught, so please consider my analysis strictly technical. Watch a short video on lateral detection with EventSentry here.

So what’s the hole? Well, the rubber ducky (mimikatz, really) requires access to an active logon session, which Angela most likely didn’t have. It looked like Joseph had been out of the office for a while, so his computer was likely either locked or turned off, rendering any attack based on mimikatz useless. Mimikatz – since it obtains passwords from memory – only works if the computer is unlocked. And had the computer been unlocked then she could have just downloaded the files from his computer – although this would have been even more risky with people walking around the office.

Cyber attacks are becoming more potent every year and are often sponsored by powerful criminal gangs and/or governments. It’s important that companies employ multiple layers of defense to protect themselves (and their customers) from these increasingly sophisticated and destructive attacks.

EventSentry is the only monitoring solution that utilizes robust agent-based technology that goes beyond logs, enabling the fusion of real-time log monitoring with in-depth system monitoring to not only detect but also react to attacks and anomalies. See for yourself and download a free evaluation of EventSentry.

Securing Exchange Server OWA & ActiveSync – Proactive Security with EventSentry

December 4, 2017December 6, 2017 ingmar.koecher 0 Comment Event Log, EventSentry, Monitoring, Security, Tips & Tricks activesync, exchange server, owa, security

Almost every company which runs Microsoft Exchange Server needs to make port 443 available to the Internet in order to provide their users access to email via their mobile devices or OWA.

Since both OWA & ActiveSync utilize Active Directory for authentication, exposing OWA/ActiveSync to the Internet indirectly exposes Active Directory as well. While user lockout policies provide some protection against brute force attacks, additional protection methods should be employed. Furthermore, password spraying attacks may be use to circumvent lockout policies – something that would be more likely to succeed in larger organizations.

With the proper auditing enabled (Logon/Logoff – Logon (Failure)) and EventSentry installed however, we can permanently block remote users / hosts who attempt to log on too many times with a wrong password. Setting this up is surprisingly simple:

Windows: Enable (or verify) Auditing
EventSentry: Setup action which creates firewall block rule
EventSentry: Setup filter looking for 4625 Audit Failure events

Bonus: This procedure works with the free version of EventSentry (EventSentry Light) and can be applied to any IIS-based web site which uses authentication.

Windows Auditing

In the group policy settings that affect the server running OWA, make sure that auditing for Failure events in the Audit Logon sub category of the Logon/Logoff category is enabled (of course you can audit success events as well). If you are running the full version of EventSentry v3.4 or later then you can verify all effective audit settings on the Audit Policy Status page for example.

Enabling correct auditing for logon failures

Creating an Action

Since event 4625 contains the IP address of the remote host, the easiest way to subsequently block it is to run the netsh command. In the management console, create a new action by clicking on the “Action” header in the ribbon and selecting the process action as its type. See the screenshot below:

The following command line will work in EventSentry v3.4 and later:

advfirewall firewall add rule name="$STRIpAddress $YEAR-$MONTH-$DAY -- automatic block by EventSentry" dir=in interface=any action=block remoteip=$STRIpAddress/32

If you are running EventSentry v3.3 or earlier then you will need to use the $STR20 variable instead:

advfirewall firewall add rule name="$STR20 $YEAR-$MONTH-$DAY -- automatic block by EventSentry" dir=in interface=any action=block remoteip=$STR20/32

The difference here is that v3.4 and later can refer to insertion string variables by name, making the action more universal and potentially applicable to any event that uses the same field name.

When this action is triggered, it will extract the IP address from the event and block it from the system entirely.

Creating a Filter

Create an event log filter which matches Audit Failure events from the Security event log with event id 4625, where insertion string 19 matches the w3wp.exe process (C:\Windows\System32\inetsrv\w3wp.exe). This ensures that only users accessing the host via the web will be subject to blocking. The screenshot below shows the configuration:

Adding a firewall rule from a 4625 audit failure event

This filter can either be added to an existing package or added to a new package that is assigned only to the Exchange server. If the filter is added to an existing package that applies to servers other than the Exchange server, then the computer field of the filter can be used to ensure the filter is evaluated only on the desired host. Select the action created in the previous step.

Since users may occasionally enter an incorrect password I recommend setting up a threshold so that remote IPs are only blocked after 3 or more failed logon attempts. Threshold are configured by clicking on the “Threshold” tab (see the blue “i” above) and an example configuration is shown below. Feel free to adjust the threshold to match your users ability to enter their password correctly :-). Insertion string 20 – which represents the IP address of this event – was selected in the threshold matching section to ensure that each IP address has its own, unique threshold. Note: The event logging settings shown are optional.

Trigger process after 3 failed logon attempts.

Save/deploy or push the configuration to the mail server.

Considerations

Triggering a system process from external input is something we should always do with caution. For example, if Windows has an upper limit to the maximum number of rules that can be added, then an attacker could launch a DoS attack IF they had the ability to launch attacks from different IP addresses. Launching a DoS attack from the same IP won’t be possible once they are blocked. You can mitigate this risk by applying a threshold to the EventSentry action calling netsh.exe, for example by limiting it to 100 / hour. This would still provide sufficient protection while also ensuring that only 100 rules could be added per hour (thresholds can be set by clicking on the “Options” button on an action). A regular audit of the netsh execution (e.g. via Process Tracking) would quickly show any sort of abuse.

Over time the number of firewall rules added to the mail server could become rather large, which is why the rules are created with a date appended. This makes managing these rules easier, and the name can also be adapted in the action by changing the “rule name” parameter. The screenshot below shows the inbound firewall rules after two IPs have been blocked:

If manual cleanup of firewall rules is not desirable or an option, then the netsh command can also be wrapped into a script which would erase the firewall rule again after a timeout (e.g. 15 minutes). The script could look like this:

"C:\windows\system32\netsh.exe" advfirewall firewall add rule name="%1 %2 -- automatic block by EventSentry" dir=in interface=any action=block remoteip=%1/32
timeout /t 900
"C:\Windows\system32\netsh.exe" advfirewall firewall delete rule name="%1 %2 -- automatic block by EventSentry"

In this case you would call the wrapper script instead of the netsh.exe process directly (General Options – Filename) and use the string below as the arguments:

$STRIpAddress $YEAR-$MONTH-$DAY

To keep things simple you can just make the script an embedded script (Tools menu) and reference the script. The timeout value (120 in the above example) is the duration seconds the remote IP will be be blocked. If you want to block the IP for an hour then you would set the timeout value to 3600 instead. When going this route I strongly suggest clearing both event log check boxes in the Options dialog of the action.

Happy Blocking!

Auditing DNS Server Changes on Windows 2008/2008R2/2012 with EventSentry

November 17, 2017November 17, 2017 ingmar.koecher 0 Comment Event Log, EventSentry, Monitoring, Pure Knowledge auditing, dns, dns auditing

In part one of this blog series we showed how to monitor DNS audit logs in Windows 2012 R2 and higher with EventSentry.

Before I continue I need to point out that DNS auditing has become significantly easier starting with Windows 2012 R2. Not only is it enabled by default, but the generated audit data is also much more granular and easier to interpret. The logged events even distinguish between regular and dynamic updates, making it easy to filter out noise. So if you’re serious about DNS auditing and have the option to update then I recommend you do so.

If you’re running Windows 2008 (R2) or 2012 then setting up DNS auditing requires a few steps. Thankfully it’s a one-time process and shouldn’t take more than a few minutes. On the EventSentry side a pre-built package with all the necessary rules is available for download and included with the latest installer.

Please follow the steps outlined below exactly as described, auditing won’t work or will be incomplete if these steps aren’t followed exactly as described below.

Enabling Directory Service Auditing

Enabling Sub Category Auditing

We first need to make sure that the new subcategory-based audit settings are enabled in group policy. If you’ve already done that, then you can skip this step and jump to “ADSIEdit”.

Since most of the steps here involve domain controllers, I recommend that you make the changes in a group policy, e.g. in the “Default Domain Controller” policy. In Group Policy Management, find an existing group policy, or create a new one, and set Computer Configuration\Polices\Windows Settings\Security Settings\Local Polices\Security Options\Force audit policy subcategory settings (Windows Vista or later) to override audit policy category settings to Enabled.

Then, navigate to Computer Configuration\Polices\Windows Settings\Advanced Audit Policy Configuration\Audit Policies\DS Access and set Audit Directory Service Changes to Success.

ADSI Edit

Open ADSI Edit via Start -> Run -> “adsiedit.msc”. If your default naming context does not automatically appear OR if the listed naming context does not include dc=domaindnszones, then select “Action -> Connect To” and connect to the appropriate naming context, e.g.

dc=domaindnszones,dc=yourdomain,dc=com

Replace the dc components after “domaindnszones” with the actual DNS name of your domain. It’s important that “dc=domaindnszones” is part of the naming context.

Once connected, expand the naming context and locate the “CN=MicrosoftDNS” container, right-click it, and select Properties. Then select Security, Advanced, Auditing and click on Add. In the resulting dialog we’ll audit the built-in “Everyone” user so that DNS changes from everyone are audited:

Name (Principal): Everyone
Apply onto:       This object and all descendent objects
Access:           Create dnsZone objects

It may seem tempting to also check the “Delete dnsZone objects”, but resist the temptation. Don’t be fooled by the term “dnsZone”, the ACE entry we just added will audit the creation of all AD DNS objects (and not just DNS zones) and log event 5136 to the security event log. In order to audit deletions as well, click “Add” again but this time configure the dialog as shown below:

Name (Principal): Everyone
Apply onto:       Descendent dnsZone objects
Access:           Delete

It’s important that the “Apply onto” is changed to Descendent dnsZone objects. This ACE entry will result in event 5141 being logged when a DNS-related directory service object is deleted. This is were things get a bit interesting though, since DNS records deleted from the DNS manager aren’t actually deleted. Instead, they are tombstoned (which is done internally by adding the dNSTombstoned attribute to the object). Only when the tombstoned object expires is it actually deleted. You can use ADSIEdit if you want to send a DNS object immediately to heaven and skip the graveyard stage.

Unlike Windows 2012 R2 and later, earlier versions of Windows are a little more verbose than you probably like when it comes to directory service auditing. For example, creating a new DNS A record in a zone will result in 4 different events with id 5136 being logged – and not just one. The events logged when adding or deleting a zone or A record are shown in the diagram below:

All events are logged under the “Directory Service Changes” category.

Testing

Before we start configuring EventSentry, we’ll want to make sure that auditing was setup correctly. On a domain controller, open the “DNS” application and either temporarily add a new A record or primary zone. You should either see a 5136 or 5137 events with the category “Directory Service Changes” logged to the security event log.

If you don’t see the events then walk through the above steps again, or reference this Microsoft article.

Configuring EventSentry

There are generally two things one will want to do with these audit events – store them in a database, email them or both. If you’re already consolidating Audit Success events in an EventSentry database then you shouldn’t have to do anything, all directory service change events will be written to the database automagically.

Database

If you only want to store directory service change events in the database (opposed to storing all audit success events), then you can simply create an include filter with the following properties:

Log:      Security
Severity: Audit Success
Source:   Microsoft-Windows-Security-Auditing
Category: Directory Service Changes

… and assign your database action to it.

Alerts

Setting up alerts using filters for when zones or records are added or removed is a little more involved than one would hope, thanks to Windows logging more than one event whenever such a change is done – as is depicted in the image above. For example, creating a new DNS record will result in 4 x 5136 events being logged, deleting will result in 3 events.

Lucky for you, we’ve analyzed the events and created a DNS Server Auditing package in EventSentry which will email you a single alert (=event) whenever a record or zone are added or removed. This package is included with all new installation of EventSentry, existing users running 3.4 or later can get it through the package update feature in the management console.

And that’s really all there is to it … if you have EventSentry installed then setting up auditing in Windows is really the only obstacle to auditing your DNS records!

EventSentry v3.4: New Security Features, Software Version Checker, Better Performance & more!

November 6, 2017November 7, 2017 ingmar.koecher 0 Comment Announcements, Event Log, EventSentry, Monitoring, RansomWare, Tools & Utilities auditing, diskspace monitoring, netflow, ransomware, UPS Monitoring

We’re again excited to announce the availability of EventSentry v3.4, the latest release of our hybrid SIEM monitoring suite.

EventSentry v3.4 delivers a number of new features to

Protect yourself against ransomware attacks
Detect lateral movement on a network with collector thresholds
Identify outdated software on your network
View detailed bandwidth utilization (requires NetFlow)
Monitor attached UPS devices
Integrate with open source solutions (Graylog, ELK, Nagios Log Server & others)

and more. We’ve also been focusing on making the data EventSentry collects more actionable and subsequently more helpful, and as result you will see additional contextual data provided with some alerts & reports, and one new search page in EventSentry.

All in all, this upcoming release has a lot of improvements in store to help you do your job better by ensuring that your network is as reliable, secure and fast as possible.

Audit Subcategories with audit success enabled, grouped by host

Ransomware

While high-profile Ransomware attacks have slowed down somewhat in recent weeks, businesses – especially small businesses – are still hit with Ransomware infections every day. Even though EventSentry is not positioned as a AV or a AntiMalware software, it does include a variety of functionality which can detect Ransomware outbreaks.

What sets EventSentry apart from AV and most AntiMalware solutions is that it looks for pattern exhibited by the Ransomware – regardless of the variant. What’s new in version v3.4 is the ability to detect changes to the MBR and bootsector as well as the ability to calculate the entropy of (changed) files.

MBR/BootSector Monitoring & Backup
Some more recent Ransomware variants modify the MBR and/or boot sector and trigger a reboot to initiate an offline encryption process. EventSentry v3.4 can now monitor the MBR and detect changes in near real-time to alert the admin when suspicious activity is occurring.

By utilizing EventSentry’s advanced filtering engine it is also possible to potentially stop the encryption process, e.g. by hibernating the infected host. EventSentry even backs up the MBR and boot sector, making it possible to repair an infected system (with a boot disk) without having to perform a full restore from backup.

File Entropy
Entropy describes the randomness of a file, essentially a metric that can help detect compressed and encrypted files.

Since most Ransomware encrypts large amounts of files, EventSentry can utilize the entropy of a file, combined with event log thresholds, to make a determination that a Ransomware infection is in progress and take corrective measures.

Lateral Movement Detection with Thresholds

EventSentry has always included agent-side thresholds in order to throttle the alert volume or detect repeated events. Because these thresholds were executed on the agents, event patterns which involved more than one host could not be detected that way.

By adding a threshold component to collector – which analyzes and processes all events in real time – we can leverage this feature to new heights and detect network-wide event-based patterns – in real time!

Collector-side thresholds are configured exactly like agent-side thresholds with one the key difference – the threshold limit applies to all aggregated events sent to the collector. Collector-side thresholds also introduce the “Group By” setting that makes the lateral movement detection possible – the ability to count unique instances of an event property, and not just the total number of events.

Some of the event-based threat patterns you can detect:

The same user logging on to multiple hosts within a specific time frame
A process spreading (trickling) across multiple hosts within a specific time frame
A user running too many processes – either on a single or multiple hosts
Authentication failures of a user on too many hosts
Too many unique logon types used by a user account

Any event property and insertion string can be used to craft thresholds – the sky is the limit.

Software Version Checker

Earlier versions of EventSentry include a substantial hardware, software and patch inventory, making it extremely easy to find out which software packages are installed on your network, but also get alerted when software is installed or removed from a server/workstation.

In v3.4 we are taking this to the next level by providing the latest version available from the publisher for a growing list of 100+ software packages so that you can effortlessly identify outdated software on your network. You can now create reports listing any software on your network which is outdated, a dashboard tile is also available. The Web Reports refresh the version info list every 2 hours to ensure all reports are accurate.

If an application you are using on your network is not currently included then simply email us the name of the software as it is detected by EventSentry (and ideally the URL where we can obtain the current version) and we will add it to our list.

64-bit Web Reports for Windows

The EventSentry web reports are now available as a 64-bit application, and upgrading to v3.4 will automatically upgrade the existing v3.x 32-bit web reports to 64-bit on 64-bit when installed/upgraded on a 64-bit version of Windows. The new 64-bit web reports will allow you to run larger reports that would not run due to limits with the address space associated with 32-bit applications.

UPS & Battery Monitoring

Any UPS directly attached to a server/workstations that is detected by Windows can now be monitored by EventSentry. The status of the UPS will show up on the host inventory page, and alerts will be generated when a host is on battery power and back on AC power. EventSentry can also initiate a shutdown when the remaining run-time or charge level falls below a certain limit.

Batteries in laptops are also detected and listed on the host inventory page (battery capacity and current charge level), but generated alerts are informational only.

User Activity Tracking

While EventSentry provides its users with a wealth of information from multiple angles, it can be tedious to piece together data from multiple reports that is associated with a specific user. Data which can be linked to a user is scattered among process tracking, file access tracking, compliance logons and other pages.

The new “User Activity” page, which is located in the “Dashboard” menu, solves this problem by displaying data from the following pages on a single page:

Logons
Processes
File Access
Active Directory Changes
Tasks
Events

The user activity page makes seeing all activity by a user as easy as never before!

Integration with third-party log management solutions

A few months ago, one of our users approached with the need to integrate EventSentry into an existing log management system which was already in place at the location where EventSentry was to be deployed. While reviewing the request we recognized that even though we position EventSentry as a one-stop log management solution with a compelling and robust web-based reporting component, an integration with other products can be helpful in some cases.

Supplement EventSentry’s built-in reporting with additional reporting
Integrate EventSentry with an existing log management solution located in a different business unit
Integrate EventSentry’s sophisticated real-time agent and deployment infrastructure with a different log management back-end

In version 3.3 and earlier, EventSentry can be integrated with 3rd party products using the HTTP, process and Syslog action. The HTTP & process action are intended to be used with ticketing systems where only a low volume of alerts are submitted while the Syslog action obviously supports submitting a high volume of events. The Syslog format was however limited to the traditional RFC 3164 format, making an integration with other log management systems difficult.

Starting with version 3.4, EventSentry now supports the following formats in the Syslog action

RFC 3164 (legacy)
Snare
RFC 5424
GELF (Graylog)
Nagios Log Server
Common Event Format (CEF)
JSON (customizable)

If a log management server you need to integrate with is not listed above but supports the JSON format, then you can craft your own JSON packet with the JSON format, also introduced in v3.4.

Disk Space Alerts

Part of the effort to make EventSentry’s alerts more actionable is reflected in our improved disk space alerts which now list the 15 largest files and folders of the volume where disk space is low. The supplemental data will in many cases be enough to immediately identify the culprit so that corrective action can be taken immediately, without the need to run disk space analyzers on the volume.

Diskspace Alert with embedded file/folder size info

Audit Policy Status

Since the introduction of the compliance tracking components, EventSentry has been recording all audit (and many other!) changes performed in Windows as part of the “Policy Changes” feature. It wasn’t however possible to see the current status of all audit categories and subcategories at a glance. Reviewing the current audit status of all monitored hosts can be important however, if only to verify that group policies are configured correctly.

In v3.4 we now have the new “Status” page available under “Compliance -> Audit Policy” which delivers information such as:

Compare/review audit settings of a particular sub category (e.g. “Registry”) among all monitored hosts
View all disabled audit settings across all or select hosts
(Re)view audit settings based on computer types (e.g. domain controllers, servers, workstations)

NetFlow Bandwidth

Our NetFlow component can now provide bandwidth visualization based on the collected NetFlow data. The information can either be accessed on the NetFlow page or as a dashboard tile. Even though bandwidth data can already be determined using SNMP, the data gathered by NetFlow should be preferred since it contains additional data not available via SNMP, such as:

Packets sent/received
Bytes sent/received
Bytes per packet
% Utilization

Bytes per packet as well as packets sent received can be used to detect anomalies, e.g. when a host sends a large amount of network packets, or network packets with large/small content.

EventSentry Blog

Category: Event Log