Snagging creds from locked machines
First off, this is dead simple and shouldn’t work, but it does. Also, there is no possible way that I’m the first one that has identified this, but here it is (trust me, I tested it so many ways to confirm it because I couldn’t believe it was true)
TL;DR USB Ethernet + DHCP + Responder == Creds
If I plug in a device that masquerades as a USB Ethernet adapter and has a computer on the other end, can I capture credentials from a system, even when locked out (yes, logged in, just locked). (..or do even more, but we’ll save that for another time, this post is already too long)
I’ll leave the setting up of the base device itself to you, but here are some links that can start you on your way:
- Debian/Jessie - https://github.com/inversepath/usbarmory/wiki/Starting#preparing-your-own-microsd-card
- Kali on USB Armory - http://docs.kali.org/kali-on-arm/kali-linux-on-usb-armory
- Resizing the SD partition - http://base16.io/?p=61
- Turtle video guides and wiki: https://lanturtle.com/wiki/#!videos.md
You do have to “Enable” the module for the first time (plugged into Internet access) to get it to actually download all of dependencies and package itself.
Then you also need to do a
opkg update and
opkg install python-openssl so that Responder will run correctly. This is only a temporary issue as the module is being fixed to include this step.
As for the USB Armory is you can either use SCP, Internet Connection Sharing, the USB host/client adapter:
The default install of Debian/Jessie doesn’t have Python installed so you will have to work through all of the dependencies (on the Kali version this is not needed) and will require Internet access to perform:
First, setting up the interface isn’t needed but it will help with consistence since each image for the Armory come with different default IP addresses and it’s good to set a solid base.
Next we set up the DHCP server:
The only special configuration here is to send the “Proxy Config” option to any DHCP clients. Why this is even a thing I have no idea, but note this line:
“DHCP has a higher priority than DNS: if DHCP provides the WPAD URL, no DNS lookup is performed.” from the Wikipedia article on WPAD
Next we set up things to automatically run. We edit the
rc.local file so that it does a few things:
- Clears out all DHCP leases and start the DHCP server. There is probably a more elegant way to do this, but because this “computer” is being plugged in and taken out pretty frequently, we could run into a max in leases but most likely the file will get corrupted at some point so we just remove and re-add it.
- Start Responder in a screen session. This way we can get logging going on the screen session as a sort of backup for the Sqlite3 database and log files that Responder creates.
To enable logging of the screen sessions (which also gives you insight into if anything went wrong), you add a
.screenrc file. There is a lot more that I put in these, mostly for aesthetics but the important pieces are these:
That’s it, you should be able to reboot your USB Armory and start picking up creds anywhere you can stick a USB in.
Everything is pretty much already done for you, the only difference is that opkg is your package manager:
Remove the symlink to /tmp/ so that the logs will stick around
/overlay/etc/rc.local file is slightly different
Why does this work?
- Because USB is Plug-and-Play. This means that even if a system is locked out, the device still gets installed. Now, I believe there are restrictions on what types of devices are allowed to install at a locked out state on newer operating systems (Win10/El Capitan), but Ethernet/LAN is definitely on the white list.
- Computers are constantly creating traffic, even if you don’t have any browsers or applications open, and most computers trust their local network for some reason (I know the technical bits on ‘why’, just complaining…)
- Network preference when there are more than gateway or network connection is based on “metrics” on Windows and a combination of metrics and “preference” on OSX, but by default “wired” and “newer/faster” always win out.
This means that by plugging in the device it quickly becomes the gateway, DNS server, WPAD server and others thanks to Responder.
The average time for freshly inserted into a locked workstation and by the time I have creds is about 13 seconds, all depends on the system. Some addition setup I used inotify to watch for a file change in the
Responder.db database and shutdown the Armory. This helps finalize file writes as well and giving me an indicator via the LED that creds were obtained.
To do that you need to install the
inotify-tools package and add the following to the
What you see in the video is the Windows 10 lock screen (Full screened fresh install VM). When the LED goes solid white the Armory has fully shutdown because of the watch script, creds achieved!.
Bring it back home and look at the results:
Sweet!! Game over!
- Windows 98 SE
- Windows 2000 SP4
- Windows XP SP3
- Windows 7 SP1
- Windows 10 (Enterprise and Home)
- OSX El Capitan / Mavericks (I was able to get creds on both of these but I’m still testing to see if it was a fluke, or my own configurations)
I still have not tested on Linux, I will make a new post on if that works. Please leave comments below if you see things I can improve upon, or errors.
USB Armory vs Hak5 LAN Turtle
- The Armory is more versitile with APT package to do more fun, definitely a great way to dev the attack. More storage (SD based) and slightly faster processor
- Hak5 LAN Turtle is MUCH easier to pass off when you are trying to plug in a device during an SE attack. It might not have the LED that the Armory does for determining when creds are achieved, but it has the added functionality of a working ethernet port, so you could get creds AND a shell. Definitely worth the extra hassel to get it working right.