Using Prey with SimpleMDM to Recover a Stolen Laptop

Monday morning, I got the call that no one wants to get: “The lock was jimmied. They got some of our computers.”

Immediately, we sprang into action. We’re big fans of SimpleMDM and Watchman Monitoring, and both of those tools came in handy. The first thing we did was check the logs from Watchman Monitoring’s client agent on the machine to see if it had checked in over the weekend.

One of the machines had checked in on Sunday! We set both to alert us if they checked in again, and logged into SimpleMDM to see if the device was checking in there, as well. We could see the one device, which gave us a couple different options: We could lock or wipe the machine and hope that it wouldn’t just end up in a landfill, or we could try to get the machine back by giving some data to the police.

I know from experience that just giving them an IP Address isn’t likely to get a good result, so we started to think what else we could we do to get the machine back? What if we could give them a location, and more information?

Screen Shot 2018 10 17 at 12 28 27 PM

Enter the Prey Project. The Prey tool works as a behind-the-scenes agent on your behalf. When it’s in regular mode, it’s not doing much. But, when you turn on Missing Mode, things get a lot more interesting. Your Mac will now check-in with nearby Wi-Fi networks, perform a full location scan and give the police something to work with. It will also take pictures with the FaceTime Camera on the Computer, and capture screenshots, giving you more material to work with:

Prey Screenshot with Wireless Networks NearbyPrey Screenshot with Map Detail

This post isn’t here to get you to buy Prey, but it’s to tell you how we got Prey installed when we didn’t have the machine in our full control.

By default, Prey requires an API key to register new machines, and their method is just “Hey! Install that at the Command Line by SSH’ing into the machine!” Which, okay, fine, that might work if you can get that far, but how’s about we do something a little bit different?

What we opted to do was to repackage the Prey installer, so that the package installer they built is stored in a common directory, (in our case, /Users/Shared) and then a postinstall script tied to the package handles the install with our API Key:


API_KEY=0xdeadbeef /usr/sbin/installer -pkg /Users/Shared/prey-mac-1.8.1-x64.pkg -target /

To build this package, we used Packages from WhiteBox. I created a new project, gave it a name (Black Widow), Included our Prey installer package to a known directory, and then add a Post Install script to invoke it using our API Key.

Screen Shot 2018 10 17 at 3 09 08 PM

Packages Post Install Script Screen

This gave me a functioning package that installed Prey and keyed it to our instance, which was great! But, how do I get it onto the stolen machine?

Enter SimpleMDM. You can use SimpleMDM to install a package onto a device, but only if you have a properly signed distribution package. The Black Widow package I made in Packages was unsigned, so now I just had to properly sign it using the prodsign command:


Screen Shot 2018 10 17 at 3 10 12 PM

This gave us a properly signed package with a valid signature:

Screen Shot 2018 10 17 at 3 17 52 PM

After uploading the package to our SimpleMDM instance, we scoped it to the machine, and waited for its next check-in:

Screen Shot 2018 10 17 at 3 19 16 PM

From there, it was a waiting game until the person who had the laptop now was back in range of the internet. Sure enough, they came back online today:

Screen Shot 2018 10 17 at 3 20 58 PM

The machine’s location and positioning information, as well as some additional detail, gave the police something to use to be a little more active on the case. We’re now waiting to hear if they’ll be able to repatriate the laptop to its owner.


Installing Ubuntu 17.10 on ESXi, from a Mac Client, to the ESXi Server

This is a guide as much for me, as much as it is for anyone else. I came to the conclusion I wanted a testbed for Reposado and Margarita, and as much as Clayton Burlison has the install of Reposado and Margarita on lock, I needed a refresher on how to create a new Ubuntu VM on my ESXi-capable Mac Mini.

First up, in VMware Fusion, connect to the server. File > Connect to Server… will give you access to the virtual machines stored on the server. You will then see a list of all the VMs currently on the server, active or not:

ESXi Host VM List

From here, you can click the + at top left to add a new VM:

ESXi Host New VM Screen

Since we are putting the VM directly on the server and not our local machine, select “Create a virtual machine on a remote server.”

ESXi Host Server Picker

Next up, you will be asked to select the server. Choose your local ESXi host.

ESXI Host Choose Host and Datastore

From here, you get to select which Datastore you want to store the new virtual machine on. If you had multiple volumes, you could select it here, whereas I just have my internal storage volume.

ESXi Host Choose HW Vers

VMware will then ask you to select a Hardware Version. There might be reasons to choose earlier versions, depending on what your local situation is like, but I’m up to date, so I’m choosing version 11.

ESXI Host Pick Network

Next, you get to choose which Network you’ll put it on. If you had multiples, you’d want to select the correct VLAN. I just have one, so I’m keeping it right where it is. You can also have VMs that have no network interface, and that’s an option here, too.

ESXI Host Pick OS

Since I’m running Ubuntu Server, 64-bit, for the final project, I’m selecting this version also for my sandbox VM.

ESXI Host Pick Firmware

If you wanted to opt to use UEFI or Secure Boot, here would be your opportunity! Ubuntu doesn’t need that, so I’m just clicking through.

ESXI Host Pick Disk Size

Last but not least, it’s time to pick your disk size. Since I’m using Reposado and Margarita, it’s a 200GB minimum to enter this party.

Now that we have our virtual machine, we need to get our copy of Ubuntu 17.10 Server. I grabbed mine from the Release Notes Page, which includes links to the Ubuntu download system. As long as you have an ISO, you should be fine to get started. Before you turn the VM on, you need to attach that ISO to the VM’s CD-ROM Drive. In the Virtual Machine’s Settings, you can select CD-ROM, and then specify the locally-stored ISO file to use as a connected volume.
VMware Settings CD ROM

Once you have selected the Ubuntu ISO file to attach as a CD, you are free to boot your virtual machine, and you’ll be presented with the next few screens as part of the process.

Ubuntu 1 Language Select

Select your preferred language for the Installer to use.

Ubuntu 2 Install Starter

Select the option to Install Ubuntu Server

Ubuntu 3 Language Select

Select your preferred language for the __operating system__ to use

Ubuntu 4 Region Select

Select the preferred region for the __operating system__ to use.

Ubuntu 5 Keyboard Config

Pick the keyboard you’re using

Ubuntu 6 User Creation

Ubuntu 7 Set Password

Set up your admin username and password. Don’t forget these. Store them in a 1Password item if you can.

Ubuntu 9 Set Timezone

Set your timezone

Ubuntu 10 Set Storage
Ubuntu 11 Volume Config

Also set up how you want the volume to be formatted. Defaults are fine, but you might choose to use Logical Volume Manager to handle your storage.

Ubuntu 12 Actually Doing Stuff

Now, it will install the OS and you’ll get an occasional screen to set up an HTTP proxy, allow security updates automatically, etc.

Ubuntu 13 Proxy

Then you can choose to install just the server, or a bunch of extra tools. Since I’m using Clayton’s guide for installing Reposado and Margarita, and it has the needed download commands, I’m just going to take the OS as it’s given to me.
Ubuntu 14 Select Additionals

More installing will occur here. Get a glass of water, you’re probably not hydrated enough today.

Ubuntu 15 More Installing

After this, you’ll be prompted to setup the GRUB Bootloader. Since this is the only Linux install on the virtual disk (It is, right? It would be really weird if it weren’t.) you can accept this configuration.

Ubuntu 17 Grub

And after that all completes, it’s time to get rolling through to your VM!

Ubuntu 18 Time to Restart

You can eject the CD-ROM on the next startup cycle.

Ubuntu 19 Logged In

Once we’ve got the box up, we want to install sshd to allow for remote access, because while it’s nice to have direct command line via the VM, ssh is so much more convenient!

We’re going to need to do a couple commands here to get it:

sudo apt-get update
sudo apt-get install openssh-server

This will install the standard openssh server and prepare it for use, allowing you to login remotely. There’s a million fiddly bits associated with opens, and you may want to customize it so that two-factor works, or machine tokens like YubiKey tokens act as your key. That’s an exercise best left for the reader. For now, I’m not publicly exposing that interface as part of this process.

Now that you have an Ubuntu 17.10 server ready to go, you can follow all the instructons of Clayton’s guide for Ubuntu 14.04 for installing Reposado and Margarita (it all still works as of 17.10!)


Slides from Munki Mistakes Made Right

Talking about the mistakes you’ve made in your career isn’t something a lot of people want to do. I spent an hour doing it today at Penn State, specifically about my Munki environments and how we’ve learned and adapted as an organization. I’ve expanded this talk since February, and it includes a conversation about how we’re slowly moving our munki repository toward cloud services like Cloudfront.

Munki Mistakes Made Right Slides


Slides from “Fighting With Physics: A Wi-Fi Workshop”

It was an incredible pleasure to present our workshop yesterday, “Fighting With Physics: A Wi-Fi Workshop”. We covered a lot of ground, answered a lot of questions, and broke a lot of old myths about Wi-Fi in the process. We’ve provided our slides below as a teaching aid to carry with you, as they often carry a lot of good and useful information for educating yourself and others.

As knowledge is like signal power, and decreases the further you get from in relation to the inverse of the square of the distance, feel free to reach out to us in Slack in #wifi, or via email, with any questions that you have, or if you need help accomplishing something in your environment.

Section 1 – RF, Wi-Fi & Jargon

Section 2 (Wide) – Mechanics and Troubleshooting

Section 3 – Wi-Fi Network Design

Section 4 – Network Security & Advanced Device Techniques