Crypto-viruses are an increasing menace that aims to turn your day the other way around, making you pay to cyber-criminals for keys that were encrypted. And what is worse is that cyber-crooks constantly keep developing new and more sophisticated ways to increase the defense of their viruses, implementing combined encryption keys that travel safely to their servers. However, there still are those ransomware viruses that send unencrypted information, allowing you, the user to sniff out traffic from your computer and with luck to get the decryption key for your files. We have designed to make a tutorial which is as simple as possible to theoretically explain how could you detect your decryption key by sniffing out your web traffic using Wireshark.
How It Works – Brief Explanation
Bear in mind that this solution is only theoretical since different ransomware viruses perform different activities on user PCs. To best clarify that, most ransomware viruses use encryption algorithm – a cryptic language replacing the original language code of the files, making them inaccessible. The two most widely used encryption algorithms are RSA and AES encryption algorithms. Both of them are extremely strong and impenetrable. In the past, most malware writers used only one encryption cipher in a special manner. The standard action for the ransomware virus was in the following consequence:
- Drop it’s payload.
- Modify the Windows Registry Editor to run on startup or after the specific action is done.
- Delete backups and perform other activities.
- Encrypt the files.
- Send the decryption key in a file or as a communication directly to the command and control (C&C) center of the cyber-criminals.
- Drop it’s ransom note and other support files that notify the user of this “complication”.
However, since malware researchers have united their resources and put a lot of effort to detect codes in the flaw or capture decryption keys and develop free decrypters, malware writers have also made quite the improvements themselves. One of those improvements is implementing a two-way encryption, using a combination of RSA and AES encryption algorithms.
In brief, they did not just encrypt your files with one of the ciphers, but now they also use a second encryption algorithm to encrypt the decryption key in a special file which is then sent to their servers. These files are impossible to decrypt, and users are hopelessly looking for alternative methods to decrypt them.
For more information on this encryption method, please visit:
Another tactic the cyber-crook “devs” started to use is a so-called cipher block chaining. This is a mode that briefly explained, breaks the file if you try to tamper with it, making any form of recovery completely impossible.
So, here is where we are. At this point, there are even new developments in the world of ransomware, which are yet to be revealed.
It is very difficult to stay ahead of ransomware, but despite all, we have decided to show you how to use Wireshark to your benefit and hopefully intercept HTTP traffic in the correct moment. However, bear in mind that these instructions are THEORETICAL, and there are a lot of factors that may prevent them from working in an actual situation. Still, it is better than not trying before paying the ransom, right?
Using Wireshark to Find Decryption Keys
Before downloading and using Wireshark – one of the most widely used network sniffers out there, you should have the malware’s executable on standby and infect your computer once again. However, bear in mind that some ransomware viruses perform new encryption every time a computer is restarted as well, so you should also configure Wireshark to run automatically on startup. Let’s begin!
Step 1: Download Wireshark on your computer by clicking on the following buttons( for your version of Windows)
Step 2: Run, configure and learn how to sniff packets with Wireshark. To learn how to start analyzing packets and check where your packets save the data, you should open Wireshark first and then choose your active network interface for analyzing packets. For most users, that would be the interface with traffic bouncing up and down on it’s right. You should choose it and click twice fast to start sniffing:
Step 3: Sniffing packets. Since ransomware viruses communicate via HTTP traffic, you should filter all the packets first. Here is how the packets look initially after you choose your interface and sniff traffic from it:
To intercept only HTTP traffic, you should type the following into the display filter bar:
→ http.request – to intercept the requested traffic
Once filtered it should look like this:
You can also filter the source and destination IP addresses by scrolling up and down and choosing one address, then right clicking on it and navigating to the following feature:
Step 4: Configure Wireshark to run automatically. To do this, first, you should go to the command prompt of your computer by typing cmd on your Windows search and running it. From there, type the following command with capital “-D” setting to get the unique key for your interface. The keys should look like the following:
Step 5: Copy the key for your active connection and create a New Text Document and in it write the following code:
→ wireshark -i 13MD2812-7212-3F21-4723-923F9G239F823(<= Your copied key) –k
You can additionally modify the command by adding the –w letter and creating a name for the file that will save it onto your computer, allowing you to analyze the packets. The result should look similarly to this one:
Step 6: Save the newly created text document as a .bat file, by going to File>Save As… and choosing All Files after which typing .BAT as a file extension, like the picture below shows. Make sure the name of the file and the location where you save it are easy to find:
Step 7: Paste the .bat file in the Windows startup folder. The original location of the folder is:
→ C:\Users\Username\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup,/p>
To easily access it, press Windows Button + R key combination and in the Window box type – shell:startup, like the picture below shows and click OK:
After your computer is restarted, if the ransomware virus encrypts your files after which generates a key and sends it to the cyber-criminals’ servers, you should be able to intercept the communication packets and analyze them.
Step 8: How to analyze the traffic?
To analyze the traffic of a given packet, simply right-click it and then click on the following to intercept the traffic:
After doing this, a Window will appear with the information. Make sure to inspect the information carefully and look for keywords that give away the encryption keys, like encrypted, RSA, AES, etc. Take your time and check the packets’ size, make sure that they are similar to the size of a key file.
Sniffing Ransomware Decryption Keys – Things You Need To Know
Like mentioned before, this tutorial is fully theoretical and in case you cannot cope with it and sniff out the keys, we strongly advise you to remove the ransomware that has infected you and attempt restoring your files using the step-by-step instructions below. Also, if you are going to attempt this method, we strongly advise you to test it out first on your computer and see the traffic. An example of how researchers have identified traffic by ransomware is the research, performed by PaloAlto network experts on Locky ransomware, which we also advise you to check.
Manually delete Ransomware from your computer
Note! Substantial notification about the Ransomware threat: Manual removal of Ransomware requires interference with system files and registries. Thus, it can cause damage to your PC. Even if your computer skills are not at a professional level, don’t worry. You can do the removal yourself just in 5 minutes, using a malware removal tool.