In a series of three articles, we will analyze the features of the ransomware families of Cryptowall, CryptoLocker and TorrentLocker. The three families have proven to be the most notorious ones, generating large amounts of money and affecting thousands of files. In the first part, we will also focus on the common features that the three threats share. Let’s begin with CryptoWall…
Ransomware has been around for many years, although the file-encrypting ransomware is quite new to the malware world. The file encryption threat was first observed in 2013, when the first variant of the CryptoLocker infections took place. Those attacks were traced back to the creator of the infamous Zeus banking malware – Evgeniy Mikhailovich Bogachev also known by his nickname Slavik.
The vicious 2013 CryptoLocker was followed by many other attacks. Some of them were part of the CryptoLocker family, while others were not known and emerged from completely new families. Some of these ransomware threats were quickly put to sleep, and others stayed active for a longer period of time.
On the verge of 2016, malware researchers at Fox IT have successfully identified three big Ransomware families, whose members have generated huge income in 2015:
Similarities in the Threat Behavior of Cryptowall, CryptoLocker, TorrentLocker
The three ransomware have many variants, most of them still being active in the wild. The attacks have happened in similar patterns and have affected countries from all over the world – mainly through exploit kits and fake emails posing as official organizations.
While the multiple ransomware variants have displayed different behavior patterns, the file types they are after and their cryptographic functionalities are often quite alike. We are going to analyze Cryptowall, and then CTB-Locker and TorrentLocker, according to the two factors listed below:
Most ransomware types are designed to place their payment instruction files in the directory of the files that are about to be encrypted. These files are typically in the form of a text, image and/or URL. Changing the background wallpaper of the infected computer to these instructions is also a common feature. In addition, a popup window may also be included to make sure the user knows his files are encrypted and he can only restore them by paying a ransom .In attacks on businesses, some ransomware types can encrypt files on drives that are network mapped on the victim’s computer.
Most ransomware families communicate with a command & control server. The communication can happen either via Tor or, in other cases, through a compromised WordPress website.
CryptoWall Threat Behavior Drilldown
Extensive research on CryptoWall indicates that it has been around since November 2013 or possibly even earlier. However, the malicious encrypting threat was active and in a prolonged development process before it became known as CryptoWall. The ransomware piece was initially known as CryptoDefense. Back then, the threat would generate the encryption keys on the local machine, something its authors fixed in the later versions.
CryptoDefense has been through many changes to evolve into the most malevolent ransomware to this date – CryptoWall 3.0.
CryptoWall’s earlier versions were set to communicate via proxy servers which would forward traffic towards the command & control server located in Tor. In newer versions of CryptoWall, the communication with the control server happened directly over the Tor network. Even though this may have been only done in a test version of the threat, it was later used by criminals as their primary method of remote communication.
In later versions, an I2P network was used. After going through many tests, the ransomware authors settled for a communication setup with two layers of proxies. These proxies are located on hacked websites. Even though these servers are quickly taken offline, they are still effective for the criminals. You may wonder why. CryptoWall only needs one connection to be able to obtain an encryption key. To say it in other words, CryptoWall doesn’t need a consistent command & control server. This feature is the primary difference between CryptoWall and other pieces of malicious software.
Read More about CryptoWall 3.0 mechanisms and how to protect your system.
CryptoWall’s Secret to Success
Whoever invented CryptoWall also created an affiliate program, thus making the ransom software accessible to other individuals. Such affiliate programs sensibly boost the income generated by CryptoWall, and are also used by other forms of ransomware.
CryptoWall Network Behavior
Once on the targeted system, CryptoWall starts looking for a functioning proxy server. When such is located, the malware will start sending its command & control server the following bits of information:
- A unique campaign identifier to determine the source of the infection.
- Its IP address to locate the infection geographically.
- Its unique identifier so that the particular infection is isolated from other infections.
After these are checked, the server will respond with:
- The location of the ransom payment page, made available for the victims to buy the decryption software.
- The victim’s country.
- The RSA-2048 public key applied for file encryption.
Once the needed information is obtained by the hackers, CryptoWall will report the exact amount of the encrypted files back to its command and control server. The server will then respond with a ransom image displayed to the user:
CryptoWall File-System Behavior
Apart from encrypting the files specified in its target file-types list, CryptoWall will also make sure to:
- Drop the lock screen image.
- Drop a TXT file containing the same instructions as on the ransom image.
CryptoWall will also disable the volume shadow copies, also known as Volume Snapshot Service, Volume Shadow Copy Service or simply VSS. The Windows Error Recovery boot screen will also be disabled. On top of it all, CryptoWall will impair the Windows updates and it will disable the security services on the victim’s machine.
This article is based on research by the Dutch company Fox IT.
To be continued…
Stay tuned! Part II is coming soon! Until then, you’re welcome to join our security forums and tell us about your experience with ransomware!
Update: Part II. CTB-Locker.
Spy Hunter scanner will only detect the threat. If you want the threat to be automatically removed, you need to purchase the full version of the anti-malware tool.Find Out More About SpyHunter Anti-Malware Tool / How to Uninstall SpyHunter
- Guide 1: How to Remove from Windows.
- Guide 2: Get rid of from Mac OS X.
- Guide 3: Remove from Google Chrome.
- Guide 4: Erase from Mozilla Firefox.
- Guide 5: Uninstall from Microsoft Edge.
- Guide 6: Remove from Safari.
- Guide 7: Eliminate from Internet Explorer.
How to Remove from Windows.
Step 1: Boot Your PC In Safe Mode to isolate and remove
Step 2: Uninstall and related software from Windows
Step 3: Clean any registries, created by on your computer.
The usually targeted registries of Windows machines are the following:
You can access them by opening the Windows registry editor and deleting any values, created by there. This can happen by following the steps underneath:
Get rid of from Mac OS X.
Step 1: Uninstall and remove related files and objects
1. Hit the ⇧+⌘+U keys to open Utilities. Another way is to click on “Go” and then click “Utilities”, like the image below shows:
- Go to Finder.
- In the search bar type the name of the app that you want to remove.
- If all of the files are related, hold the ⌘+A buttons to select them and then drive them to “Trash”.
In case you cannot remove via Step 1 above:
You can repeat the same procedure with the following other Library directories:
Tip: ~ is there on purpose, because it leads to more LaunchAgents.
Step 2: Scan for and remove malware from your Mac
Remove from Google Chrome.
Step 1: Start Google Chrome and open the drop menu
Step 2: Move the cursor over "Tools" and then from the extended menu choose "Extensions"
Erase from Mozilla Firefox.
Step 1: Start Mozilla Firefox. Open the menu window
Step 2: Select the "Add-ons" icon from the menu.
Step 3: Select the unwanted extension and click "Remove"
Uninstall from Microsoft Edge.
Step 1: Start Edge browser.
Step 2: Open the drop menu by clicking on the icon at the top right corner.
Step 3: From the drop menu select "Extensions".
Step 4: Choose the suspected malicious extension you want to remove and then click on the gear icon.
Step 5: Remove the malicious extension by scrolling down and then clicking on Uninstall.
Remove from Safari.
Step 1: Start the Safari app.
Step 3: From the menu, click on "Preferences".
Step 4: After that, select the 'Extensions' Tab.
Step 5: Click once on the extension you want to remove.
Step 6: Click 'Uninstall'.
A pop-up window will appear asking for confirmation to uninstall the extension. Select 'Uninstall' again, and the will be removed.
Eliminate from Internet Explorer.
Step 1: Start Internet Explorer.
Step 2: Click on the gear icon labeled 'Tools' to open the drop menu and select 'Manage Add-ons'
Step 3: In the 'Manage Add-ons' window.