Flog of ransomware is by far today’s biggest computer security concern. Threat actors have stepped into the crypto realm & thrown down the gantlet to antivirus labs hat are still figuring out ways to do away with his challenge.

Ransomware based on open source code, especially variants based on Hidden Tear continue to proliferate to spread consternation among masses and hence reap monetary gains.

The ease of availability and deployment of this open source Ransomware code allows even novice developers to extort victims with this ransomware family. The first few Hidden Tear-based variants didn’t stray far from originals. But it comes as no surprise that the developers of ransomware keep building on the released code with minor tweaks to create improved variants.

Hidden Tear Ransomware- Threat Behavior

Hidden Tear is the first open- source Ransomware Trojan that targets Microsoft windows operating system. During its release, the Ransomware was advertised as being created “only for educational purposes”. However, these were quickly abused by cyber criminals.

HiddenTear Ransomware family leverages AES (Advanced Encryption Standard) algorithm to encrypt certain types of files. Originally known as Rijndael, this algorithm is symmetric, that means that encryption and decryption keys are identical for this Ransomware. The key can be 128, 192, or 256 bits long.

Files encrypted by this Ransomware gain a file extension that varies based on its variant. Hidden Tear has an encryption backdoor, i.e. the encryption key is transmitted to attacker’s remote server so that it’s only available to the operator.

To recover the encrypted data, the victim needs to have a specially crafted decryption program and the secret key at their disposal. These two prerequisites are the objects of negotiation, or rather, a bargain between the perpetrator and the user.

Victim is informed about the encryption via a ransom note. The note claims to provide a document with detailed recovery instructions and relevant hyperlinks once the ransom is paid. However victims are recommended not to fall in the trap as they are often ignored once the ransom is paid.

Hidden Tear Ransomware Distribution

Owing to the light weight payload of only 12KB, the infection is many cases is distributed via phishing emails that contain booby-trapped attachment.

Threat actors abuse macros to spread the dangerous infection. Disabled by default, user is prompted to enable macros once the file is opened. If enabled the script automates the installation of this pernicious malware.

Hidden Tear also exploits users via malevolent advertisements, bundled programs fake updates, unprotected P2P networks, torrents etc. Hidden Tear ransomware needs only one click to infect the machine. Hence prevention is crucial in this case.

HiddenTear Ransomware Variants

Since the deployment of Hidden Tear Ransomware code in GitHub, threat actors have evolved multiple variants of this menace. Extensive flexibility of the code makes it trivial for anybody interested to devise a custom variant of the program.

Few recent & perilous variants of this Ransomware threat include:

EnybenyCrypt Ransomware: Utilizes AES-256 algorithm to lock files with a .crypt888 extension.

Donut Ransomware

Hidden Beer Ransomware: AES cipher is leveraged to encrypt files with .beer extension. It behests ransom of $100 dollar payment in Bitcoin for recovering files.

EbolaRansomware: It appends all files with .101 extension. It drops a ransom note on desktop background to inform users about the encryption.

Open-source ransomware have raised a red flag in the cyber security community. Hidden Tear Ransomware is exploited by cyber crooks who used the public source code, modified it and attacked users.

Hence users are recommended to maintain regular data backup and store them on a remote server or unplugged storage devices to be on a safer side.

Threat Summary

Name: Hidden Tear

Targeted Operating System: Windows

Category: Ransomware

Symptoms: User’s files are encrypted. All locked files are appended with certain extensions after the encryption and hence cannot be accessed by the user.

Guide to remove Hidden Tear Ransomware

STEP A: Remove the services installed by Hidden Tear Ransomware from the System using Safe mode with Command Prompt

Windows 7/ Vista/ XP

1. Click on Windows icon present in the lower left corner of the computer screen.
2. Select and click Restart.
3. When the screen goes blank, keep tapping F8 key until you see the Advanced Boot Options window.
4. With the help of arrow keys on keyboard, Select Safe Mode with Command Prompt from the list and press the Enter Key. The system will then restart to Safe Mode with Command Prompt.
5. Click on the username and enter the password (if any).

Windows 10 / Windows 8

1. Press and hold the Shift Key and simultaneously click on the windows icon present in the lower left corner of your computer screen.
2. While the Shift key is still pressed click on the Power button and then click on Restart.
3. Now select Troubleshoot → Advanced options → Startup Settings.
4. When the Startup Settings screen appears which is the first screen to appear after restart, select and click on Enable Safe Mode with Command Prompt. The system will then restart to Safe Mode with Command Prompt.
5. Click on the username and enter the password.

Once the system starts, ensure to use an account with administrative privilege to access Safe Mode with Command Prompt.

After the user enters admin credentials, Command prompt window is displayed wherein you are entitled to enter the below commands:

1. Type the command “sc delete Hidden Tear Ransomware” in the command prompt and press Enter.
2. Type “exit” to exit the command prompt and restart the system in safe mode with command prompt.

STEP B: Restore your system files and settings

Method 1 using Control Panel

1. Click on the ‘Start’ button on the taskbar. This will open the Start menu.
2. Click on the ‘Control Panel’ button in the Start menu. This will open the control panel window.
3. In the Control Panel window, click on the ‘View by:’ button on the top right. Select the Large Icon option
4. In the control Panel window click on the ‘Recovery Icon’. This will open a window that will ask ‘Restore the computer to an earlier point in time’.
5. Click on the ‘Open system restore’ button. This will open the ‘system restore ’window where you need to click on the Next Button.
6.  Select the restore point that is prior the infiltration of Hidden Tear Ransomware. After doing that, click Next.
7. This will open the ‘Confirm your restore point’ dialog box. Click on Finish button. This will restore your system to a previous restore point before your system was infected by Hidden Tear Ransomware.

Method 2 using Command Prompt

1. Type cmd in the search box and click on the command prompt to open the Command Prompt window. box and clicking on it.
2. Once the Command Prompt window shows up, enter cd restore and click Enter.(Ensure that you in the system32 directory of Windows folder in C Drive)
3. Now type rstrui and press Enter again.
4. When a new window shows up, click Next and select your restore point that is prior the infiltration of Hidden Tear Ransomware. After doing that, click Next.
5. This will open the ‘Confirm your restore point’ dialog box. Click on Finish button. This will restore your system to a previous restore point before your system was infected by Hidden Tear Ransomware.

Method 3 : Directly type ‘rstrui’ in the search box

1. Type ‘Rstrui’ in the search box present on the task bar. This will open the System restore dialog box.

Continue to follow steps 4 & 5 of Method 2 to restore the System Files and settings.

Tips to prevent your computer system from getting infected –

1. Keeping the Operating System Updated- In order to remain protected and avoid such infections, it is recommended to keep your Operating System updated by enabling the automatic update on your system. The systems with outdated or older versions of Operating System become an easy target for the attackers.
2. Resist clicking on spam emails – One of the major techniques used for malware distribution is forwarding spam emails to the user. The system gets infected as soon as the user clicks on the attachment. These mails appear to be genuine, so be aware and resist falling for these tricks.
3. Keep an eye on third party installations- It is quite important that you take due care while installing any third party applications for they are major source of such infections. Such malware programs come bundled with the free applications thereby requiring the user to remain cautious.
4. Regular periodical backup- In order to keep your data and files safe, it is recommended to take regular back up of all your data and files either on an external drive or cloud.
5. Use Anti-Virus Protection- We strongly recommend the use of antivirus protection/internet security in your PC like Avira and Kaspersky Labs Inc so that it remains safe.
6. Enable the Ad Blocker/Popup Blocker in your browser- Enabling the popup blocker/ ad blocker in your chosen browser will help you to stay protected from annoying adware.