How to Hide Executable Code in a Text File using Cloaking and Alternative Data Streams

Hacker Basics: How to Hide an Executable File Inside and Text File

Did you know that hackers can hide an executable file inside of a text file using a technique that uses something called data streams to trick a computer system from seeing text and or executable written in an alternate data stream inside a common text file.

I was pretty impressed the first time I watched someone demonstrate this. I was like, NO WAY! I really thought that this was some wizard level hacker stuff.

I’m no wizard level hacker, although I aspire to be, but I should be good enough to show you how to embed a simple calculator app inside a text file using an alternate data stream.

A big thank you to Cyber Security Expert, Malcolm Shore who presented a similar example in his Cyber Security Foundation online course I recently completed.

How Do Alternate Data Streams Work?

Way back in the old Wild West days when we had the DOS operating system, files used to be simple strings of data. Files are read btye by byte.

Later, in the NTFS file system, files are complex structures. NTFS files at a minimum contain a section called $Data where data is read by an application. $Data is the Data Stream.

Files may have many other sections or streams other than just the $Data section. This is what we call “Alternate Streams”.

THIS IS IMPORTANT: Windows only recognizes data in the $Data section so any data we put in an alternate data stream is not read by the Windows Operating System. We cloak data we want to hide in an alternate data stream. That’s the basics of how this works.

The data we are hiding could be a malicious malware payload or encrypted espionage message for our spy ring but in this example, it is just the simple calc.exe file you can find on any Windows PC for the last 20+ years.

Creating an Alternate Data Stream in a Text File

The screenshot below shows the three (3) files we’ll be using in this demonstration.

  • Simple text file with some string data.
  • calc.exe application or executable binary file
  • Secret text file with some string data

We can see the size of the text file is just 1 KB and the calc.exe file is 897 KB.

If we open the text-data.txt file with Notepad we’ll see just a simple line of text and the same with the secret-data.txt file.

To hide our secret message inside the the text data file, we’ll use this command line command.

C:\text\>type secret-data.txt > text-data.text:hidden.text

Screenshot of Alternate Data Stream: Insert Hidden Text

Below is a screenshot of the command line command “type” that we used in this example to insert our secret-data.txt file into an Alternate Data Stream inside of another text file.

If we type the command “more” we can look for the secret message.

The screenshot below shows the text file that contains our hidden text being opened in Notepad where we can’t see the hidden text we saved to the file. If we type the command line command below, we can read the hidden text we wrote to our Alternate Data Stream by keying in on the specific data stream.

c:\test>more < text-data.txt:hidden:text
Screenshot: Display hidden text in a text file.

Hiding an Executable Inside a Text File

Hiding an executable file inside a text file using the exact same Alternate Data Stream technique we just used in the the Secret text file example above but this time we’ll simply replace the Secret text file with the Windows Calculator application executable file.

The screenshot below shows the command line command to save the calc.exe file in an Alternate Data Stream in side our target text file.

Notice this time, the Alternate Data Stream is named “mycalc.exe”. Don’t get to hung up on this, it is just a name that is basically meta data that is saved with the data that we can use to filter the data we get out of the file. I hope that makes sense.

Important to note at this point that the file sizes didn’t change when we inserted the calc.exe file. It is still showing 52KB.

How to Execute a File Saved in an Alternate Data Stream

To execute a file you’ve stored in an Alternate Data Stream, we’ll need to use the wmic command as is done in the following example.

c:\test>wmic process call "c:\test\text-data.txt:mycalc.exe"

As you can see from the working example above, I was able to embed the calc.exe file inside as well as text file and a secret message.

If the data is text we just need to indicate which stream we saved the data in to retrieve it.

If the data we hid was an executable file, we’ll need to use the Windows “wmic” command line command to call the executable from inside the text file by keying in on the Alternate Data Stream name.

In summary, the technique is crazy easy to pull off without any 3rd party hacking tools. It just requires a little Windows Operating System inside knowledge but is something every good hacker should know.

I hope this helped somebody!
~Cyber Abyss

Google Dorking? Yeah, it’s a thing. Search Google for Hidden Files

Let me start by saying the title might be a little off, as the files are not technically hidden as much as they are obscure.

While most of us would consider ourselves pretty good Googler searchers these days but the truth is, there is so much more to Google searching than meets the eye.

Introducing… “Google Dorking”

Yes, I said it Google Dorking and it’s not what you might think. Sounds dirty, right? It’s not just me. LOL

Google Dorking also known as Google hacking is about searching Google in a way that filters and brings all sorts or OSINT and InfoSec goodies floating to the top.

Think Before You Dork!!!

Although the information my be available on Google, it does not mean you can use that information to try and hack or gain unauthorized access to a system or individual computer.

Hacking is illegal, don’t do it, don’t talk about it.

With that being said, please be careful, be responsible and please enjoy these Google Dorking Examples for educational purposes.

Searching Google for user names and password in log files

allintext:username filetype:log

Searching Google for Open FTP Servers

intitle:"index of" inurl:ftp

Searching Google for Open Web Cams

Intitle:"webcamXP 5"

inurl:view/index.shtml 

Searching Goolge for Database Passwords

db_password filetype:env

Searching Google for Git-hub Resources

filetype:inc php -site:github.com -site:sourceforge.net

Searching Google for PHP Variables

filetype:php "Notice: Undefined variable: data in" -forum

Search Google for Server Configuration Files

intitle:"WAMPSERVER homepage" "Server Configuration" "Apache Version"

Search Google for Nessus Scan Reports

intitle:"report" ("qualys"|"acunetix"|"nessus"|"netsparker"|"nmap") filetype:pdf

Search Google for Networking Xls Files

ext:xls netoworking

Search Google for FrontPage Servers w/ Admin Info

"#-Frontpage-" inurl:administrators.pwd

Search Google for Unprotected Cameras

inurl:view/index.shtml

Search Google for Hidden Login Pages

Username password site:com filetype:txt DomainName.com

Google Dorking Video by Null Byte

Hope this helps somebody!
~Cyber Abyss

How to Retrieve Logged in User from a Windows PC using VBScript WMI

If your in need of finding out who is logged on to a specific Windows PC on your network, run the VBScript below.

When executed, you’ll see a message box with the name of the account currently logged in the computer specified.

The VBScript Code

To use this code, copy it in to a text file and save it with a .vbs file extension for VBScript. Once you have the .vbs file, double click on it and you should get a message box with the names of the logged in user on the specified Windows PC on your network.

Function GetLoggedinUser(strComputer)
	Set objWMIService = GetObject("winmgmts:" _
		& "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2") 

	Set colComputer = objWMIService.ExecQuery _
		("Select * from Win32_ComputerSystem")
	 
	For Each objComputer in colComputer
		Wscript.Echo "Logged-on user: " & objComputer.UserName
	Next	
	
End Function

' Pass a . to run this on your own PC or add a string value name for PC on your network
'strComputer = "XPS1234"
strComputer = "."

call msgbox(GetLoggedinUser(strComputer))

Stay tuned for more scripts in upcoming blog posts!

Hope this helps somebody!
~Cyber Abyss

InfoSec Tip: What’s in those web server 404 NOT FOUND errors?

Catching Bad Guys using Web Server 404 Errors!

404 NOT FOUND pages in your web server logs are often the earliest sign of surveillance, foot printing or reconnaissance.

This probing event I caught was using the IP, bypassing DNS while probing for non-existent file called “/admin/config.php” all the way from Ramallah Palestine. #Infosec#OSINT#cybersecurity

Hope this helps someone!

Regards,
Rick

3 Low Cost Ideas to Address RDP Brute Force Attacks on Your Windows Web Server

Its late at night, I’m remoted in to my Windows web server. I’m reviewing the event logs and see something suspicious. Audit failures in the Security event logs.

The next 7 hours had me consumed in learning everything I can about “Brute Force RDP Attacks” and try to apply it to my server ASAP.

Before I go any further, I want to reiterate that this a hobby server I run. This is not a server I work on for my day job in a large enterprise environment. Hence the focus on low cost solutions.

First, Remote Desktop Protocol (RDP), is probably one of the most commonly unsecured items on Windows web servers which is also why your server is going to be relentlessly pounded by scanning tools and hackers trying to access your server via RDP, usually via port 3389.

Video: Brute Force Attack with Hydra Hacking Tool

I could just block port 3389 and move on with my life but I personally prefer to access this particular server via RDP to handle administrative tasks. Everything else is done via FTP or telnet.

I run all my hobby servers on a super tight budget. This article will discuss what I learned and how I applied that knowledge to mitigate some of the risk associated with managing Windows servers exposed to the Wild Wild West (WWW) with RDP connections using techniques that are no cost except for your time to implement.

Low Cost Ideas for Mitigating RDP Brute Force Attacks on Your Windows Servers

  1. Use Strong Passwords
    • Strong passwords are your first and best defense for any RDP brute force attack.
      • Use a password with a length or 12 character or more.
      • Don’t use words that can be found in a dictionary
      • Use a combination of UPPER CASE, lower case, numbers and special characters
      • Be Social Media aware! Don’t use friends, family, pets or info that could be derived from Social Media posts.
  2. Clean Up Old User Accounts
    • Make sure only the accounts you need are on your server.
    • Fewer accounts reduces possible attack vectors.
    • Also validate the level of access of the accounts on your server.
  3. Update Windows Firewall Rules
    • Exclude IP Ranges for Countries with highest amount of hacking.
    • See steps below for updating your Windows Firewall configuration to block IP ranges for China, Russia and North Korea.

Before You Mess with Your Firewall

The PowerShell script I cover below worked great but then decided to build a firewall rule manually for South American IP addresses and re-learned a very important lesson about working with Firewalls.

A word of caution: Don’t build your Firewall IP restrictions manually.

Always script them out in PowerShell. If you’re not 100% awake and paying attention, you will find yourself blocked out of your server and kicking yourself in the ass like I did.

Thankfully, I have a great hosting company, AccuWebHosting, who has been able to un-do all my screw ups so far. I’ve used them happily for many years and highly recommend them. I pay about $500 a year for a decent Windows server VPS with great support.

Use Windows Firewall to Block IP Ranges for China, Russia and North Korea and many others.

The steps to block IP ranges using Windows Firewall are pretty simple.

  1. Create a directory for working with PowerShell and PowerShell Scripts.
    • Example: C:\ip-security
  2. Go to this page click on Step 2 link to download your PowerShell scripts zip file.
  3. Extract contents of the the ip-security-package.zip file to your “C:\ip-security” folder.
    • You folder should look like this:
  4. Open PowerShell from the Command Line as an Administrator so you’ll have the correct rights to make changes to the Windows Firewall
  5. Run this command to make sure PowerShell is in the right mode
    • “Set-ExecutionPolicy Bypass”
    • Type “Y” when prompted to access the change
  6. Type the following commands to import the IP Range Exclusions in to Windows Firewall.
    • Import-Firewall-Blocklist.ps1 -inputfile china.zone.txt
    • Import-Firewall-Blocklist.ps1 -inputfile russia.zone.txt
    • Import-Firewall-Blocklist.ps1 -inputfile northkorea.txt
  7. You should now have IP blocks in your firewall.

If you’ve done these three things, your web server is better prepared than most.

Some Closing Thoughts on Web Server Security

Security on the internet is hard and ever changing. Running your own server for your hobby or side hustle can be done but can be very frustrating and overwhelming at times. Do as much of what I covered as you can.

We covered a few options above, but if you get nothing else from this article, make sure your passwords are long and hard to guess as this is the last defense before a bad guy gets access to your system.

From meetings I’ve been in with Enterprise engineers, passwords of 12 characters or more are best. Rainbow hash attacks can typically get most common passwords less than 12 characters. Scary, right?

Don’t use passwords made from words that can be found in a dictionary and now with the new world of social media, avoid using your kids, significant other or pet’s name or other references that can be guessed from online posts.

In one of the attacks that prompted me to write this article, one attacker used my youngest Son’s full name. I don’t use Facebook anymore so there only a few places you could go to figure that out.

I hope this story helps someone else on their IT Journey.

Regards,
Rick Cable
Lost in the Cyber Abyss

References:

https://www.gregsitservices.com/blog/2016/02/blocking-unwanted-countries-with-windows-firewall/

http://www.ipdeny.com/ipblocks/

https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.security/set-executionpolicy?view=powershell-6