Using your service desk system to track and schedule important & security-related tasks

September 19, 2018September 19, 2018 / Daniel S / Leave a comment

Most IT departments would have some type of service desk system in place, but are they using it for more than just the basic support scenarios and change control?

Any modern service desk system should also be able to schedule tickets and change requests, and perhaps even perform more advanced workflow functions.

I’m using the excellent Freshservice SaaS app, and I’ve recently been taking advantage of the scheduling and workflow features to automatically generate tickets to:

Remind about domain registration renewals
Remind about SSL certificate expiry
Ensure that the Domain’s krbtgt account password is rotated frequently
Schedule password changes for the Azure AD Connect seamless single sign-on domain account AZUREADSSSOACC$
Schedule manual password changes for service accounts that don’t support the use of Managed Service Accounts (or gMSAs)
Schedule guest Wi-Fi network key rotation

Moving these types of tasks out of the minds and calendars of individual staff is important. It ensures that these sometimes critical actions continue regardless of staff turnover.

Another benefit is that within each scheduled ticket you can include clear written instructions on how to carry out the task. You also gain a long-term audit trail and notes for each time the task was carried out.

One final related note – you could also look into pointing your email security and other notifications to the service desk if you aren’t already doing so. Again, you’ll get a clear owner for each outstanding task, an audit trail of what was done, and you can assign priorities and SLAs. For example:

Email administrator notifications (quarantine notifications, content notifications, etc)
Print device consumable alerts

Let me know what you think in the comments below. Do you have any additional useful tips?

Fix: Can’t install iManage FileSite 64-bit due to installer complaining about mismatched ‘bitness’

February 5, 2018February 5, 2018 / Daniel S / 2 Comments

Testing FileSite 64-bit, I ran into an issue on my own PC. I had 64-bit Office 2016 installed, but the FileSite installer refused to continue and presented me with the following message:

Dialog box: iManage Work FileSite (x64) requires that your computer has matching bitness with all Microsoft Office producs as well as any other iManage Desktop clients, Aborting Installation...

In an attempt to locate the cause of the issue, I fired up the trusty Sysinternals Process Monitor, and set up a filter to capture activity from msiexec.exe. I then further refined that filter to capture only RegQueryValue operations, and re-ran the installer.

Sure enough, Process Monitor picked up some instances of the installer reading from the registry to determine the ‘bitness’ of Office and other iManage products. In my case, there was a lingering registry entry that led the installer to conclude that I still had the 32-bit version of FileSite installed:

A screenshot of Process Monitor, showing a registry key at HKLMSoftwareWOW6432NodeInterwovenWorksiteClientCommonInstallRootbitness with a value of "X86"

Because I didn’t have any iManage products installed at the time, it was safe for me to delete the entire HKLM\SOFTWARE\WOW6432Node\Interwoven reg key.

The installer then ran successfully after this. Thank goodness for Sysinternals by Mark Russinovich.

Internet Explorer’s dangerous default behaviour when a PAC/WPAD file directs the browser to BYPASS the proxy

January 19, 2018January 22, 2018 / Daniel S / Leave a comment

Today I became aware of this interesting/potentially dangerous default behaviour in Internet Explorer when you use a proxy configuration PAC/WPAD file. Yes, I know that WPAD is a bad idea for other reasons, too.

To quote the IEInternals blog: “One sometimes surprising aspect of proxy scripts is that they impact the Internet Explorer Security Zone determination…. if a proxy script is in use and returns DIRECT, the target site will be mapped to the Local Intranet Zone.”

This is a non-issue if your PAC file only bypasses the proxy server for internal sites, but if you for some reason need to bypass the proxy for an external site, it’s suddenly running outside of Protected Mode and is without the protections in place that the default Internet Zone settings offer.

Screenshot of a PAC/WPAD file showing the FindProxyForURL function with a single example condition to bypass the proxy for example.contoso.com. In this case, the code returns the string "DIRECT" if the url matches https://example.contoso.com*

Here’s a test with the settings in the default state, and the PAC file instructing all HTTPS traffic to BYPASS the proxy:

Screenshot of Internet Explorer, browsed to https://www.google.com.au, and File, Properties in Internet Explorer showing that the current zone is "Local Intranet"

The solution to this is to ensure that the following box is un-checked.

Screenshot of the dialog box that appears in Internet Explorer when you go to Internet Options > Security (tab) > Local Intranet > Sites (button). Showing the "Include all sites that bypass the proxy server" option is currently checked/ticked

This setting can be found in Internet Explorer under Internet Options > Security (tab) > Local Intranet > Sites (button)

In a corporate environment, you can disable this “feature” via GPO, under Computer/User Configuration > Policies > Administrative Templates > Windows Components > Internet Explorer > Internet Control Panel > Security Page > Intranet Sites: Include all sites that bypass the proxy server

Disabling via GPO will result in the checkbox being greyed out:

Another test run after making the above changes, showing the correct zone assignment:

Screenshot of Internet Explorer, browsed to https://www.google.com.au, and File, Properties in Internet Explorer showing that the current zone is "Intranet", and Protected Mode is ON

Post-publishing footnote:

I discovered that you also need to ensure that Automatically detect intranet network is not checked.

Screenshot of the dialog box that appears in Internet Explorer when you go to Internet Options > Security (tab) > Local Intranet > Sites (button). Showing that 'Automatically detect intranet network' and 'Include all sites that bypass the proxy server' are greyed out and un-checked

This can be achieved via GPO under Computer/User Configuration > Policies > Administrative Templates > Windows Components > Internet Explorer > Internet Control Panel > Security Page > Turn on automatic detection of intranet (set to disabled)

Automatically Create 40 Event Viewer Custom Views

November 7, 2017November 7, 2017 / Daniel S / Leave a comment

I still find Custom Views useful when troubleshooting on individual workstations, and I’d recently been wondering if it was possible to push them out via GPP or similar. I started creating some views manually, as a test, but it was taking too long.

I’d recently been working on implementing Palantir’s WEF/WEC setup, and wondered whether I could leverage their legwork to automate the creation of these custom views.

The script I came up with took a fraction of the time to write, as opposed to the manual method. It does the following:

Downloads the Palantir ‘windows-event-forwarding’ repo in ZIP format into a temporary folder
Extracts the Event Log query out of each file in the ‘wef-subscriptions’ folder, and
turns it into an appropriately-named custom Event Viewer view (XML) file in %PROGRAMDATA%\Microsoft\Event Viewer\Views

2017-11-07 16_51_46-Event Viewer

I love how simple PowerShell makes it to work with XML.

The script needs to be run as an admin in order to create the view files in %PROGRAMDATA%, unless you change the output path in the $templateStoragePath variable. It’ll also need to be able to connect to the Internet to download the ZIP file from GitHub.

I’ve started storing my scripts in my PowerShell GitHub repo rather than as Github Gists, and it’s harder to embed them on wordpress.com. View the code via the link below:

https://github.com/dstreefkerk/PowerShell/blob/master/Create-EventViewerCustomViews.ps1

Mitigate commodity malware attacks with Windows Firewall rules

October 24, 2017October 24, 2017 / Daniel S / Leave a comment

There’s so much that can be done with the built-in Windows tools to prevent commodity malware or ransomware attacks before you even spend a cent on 3rd party tools. All of these things can (and should be) combined to create a good multi-layered strategy:

Restricting use of administrative credentials
Ensuring that UAC is enabled
Using Application Whitelisting (SRPs, AppLocker, Device Guard)
Associating malicious filetypes (such as .JS) with Notepad through Group Policy
Controlling or preventing the execution of Office macros
Using newer Office features to prevent execution of macros in files downloaded from the Internet
Patching applications, keeping them up-to-date
Preventing script hosts and command interpreters from connecting to the Internet

The last point has been on my to-do list for some time now. I was again reminded of it the other day while watching Sami Laiho’s recent Microsoft Ignite session about PAWs.

A lot of email-delivered malware begins with a macro or via DDE attack, and then attempts to connect to the Internet to pull down more nasties.

Today I came across this great blog post by Branden, in which he describes a handy method to prevent applications from communicating with hosts out on the Internet, while still allowing them to communicate within the internal network.

I set about manually creating a list of outbound firewall rules, including a whole bunch to mitigate the application whitelisting bypasses highlighted by the brilliant Casey Smith here. Doing this via the GUI is painful, and I wouldn’t wish it on anybody:

A listing of outbound firewall rules created in Windows Firewall with Advanced Security

Here’s a screenshot of PowerShell connecting to the web, before putting the firewall rule in place:

A PowerShell prompt, running Invoke-WebRequest to google.com, and showing a successful request

And here’s one taken after I enabled the firewall rule:

But PowerShell can still connect to an internal web server:

A PowerShell prompt, running Invoke-WebRequest against an internal HTTP server. Showing a successful response

There are obviously going to be exceptions to these rules, for example to enable your IT staff to access Azure AD or other cloud-based services via PowerShell, but those things should be done from dedicated administrative hosts anyway. This ruleset is more for the general user population.

When the time came to think about sharing this ruleset here on my blog, I discovered that it’s possible to export the rules from the registry and re-import them elsewhere, however that has its own potential issues.

I instead created the following PowerShell script that will generate all of the appropriate rules using the New-NetFirewallRule cmdlet. It’s also much easier to review this script to see what it does, rather than read a registry export file.

You could extend this script to apply the rules directly to the appropriate GPO by using the -GPOSession parameter on the New-NetFirewallRule cmdlet.

As usual, run at your own risk, and test thoroughly before deploying:

The embedded Github Gist doesn’t show up on mobile devices. Here’s a direct link to the raw script file: https://gist.githubusercontent.com/dstreefkerk/800a9e0a22a6242a28b058be423cf0ba/raw/c2be1189f88fb5ad9acaab708ad985587a576ceb/Create-MitigationFirewallRules.ps1

Automatically drop your Privileged Access Workstation off the network while it’s unattended

October 20, 2017October 20, 2017 / Daniel S / Leave a comment

“One of my favorite hobbies is hunting sysadmins” – Hacker of Hacking Team’s network

I only periodically log in to my Privileged Access Workstation to carry out administrative tasks. Although I have restrictive policies applied and Windows Firewall locked down, there’s no reason for that machine to be on the network while I’m not actively using it.

In an attempt to address this, I created two simple scheduled tasks:

1. Disable all NICs when workstation is locked

2. Enable all NICs when workstation is unlocked

Note that these depend on the correct audit logging being enabled on the machine in question, otherwise these tasks won’t trigger:

It also depends on how you use your PAW. If you regularly log out rather than shut down, you will need to add additional triggers to the tasks to handle the log off/log on events.

Import these tasks into Task Scheduler and use them at your own peril. You may run into issues if you don’t store any cached logons and simultaneously require a domain controller to be accessible at logon.

User Error

Ramblings of a tinkering SysAdmin