RotorCrypt Ransomware Removal – Restore .Black_OFFserve Files

RotorCrypt Ransomware Removal – Restore .Black_OFFserve Files

RotorCrypt ransomware image

Our RotorCrypt ransomware removal guide shows how computer users can restore their computers from the dangerous virus. It alters important settings on the system and can lead to further infections. Read our in-depth article to learn more about it.

Threat Summary

TypeRansomware, Cryptovirus
Short DescriptionThe RotorCrypt ransomware is a dangerous virus that assigns .Black_OFFserve extension to the compromised files. The victim’s system is also modified and additional malware can be instituted in them.
SymptomsThe victims will notice that a large portion of their data is going to be encrypted with a powerful cipher and renamed using a template extension. They may also experience significant performance issues, application failure and other types of damage.
Distribution MethodSpam Emails, Email Attachments
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User ExperienceJoin Our Forum to Discuss RotorCrypt.
Data Recovery ToolWindows Data Recovery by Stellar Phoenix Notice! This product scans your drive sectors to recover lost files and it may not recover 100% of the encrypted files, but only few of them, depending on the situation and whether or not you have reformatted your drive.

RotorCrypt Ransomware – Ways of Distribution

The RotorCrypt virus is a well-known example of the the ransomware family that shares the same name. A new virus samples has been identified that appears to be a customized version of prior code.

The current wave of RotorCrypt ransomware is primarily distributed using the traditional delivery methods. Depending on the attack campaign the criminals can opt to use email spam messages by taking advantage of different social engineering tricks. The hackers usually use templates that utilize the spread mechanics. The criminals behind the RotorCrypt virus specifically carrying the .Black_OFFserve extension strain can depend on several tactics when distributing the malware messages:

  • File Attachments — The virus files can be attached directly to the messages as attachments under different names. The victims may be coerced into opening them up by masquerading as useful software or utilities. Advanced tactics use password-protected archives which contain the ransomware strains.
  • Hyperlinks — The criminals can embed links that lead to the Rotorcrypt ransomware executable files. They are usually disguised as password reset links, login pages, confirmation dialogs or other related parts of popular web services.
  • Infected Documents — The criminals can utilize virus documents that may include rich text documents, spreadsheets or presentations of user interest. Once opened the victims will see a notification prompt. It asks them to enable the built-in macros (scripts). If this is done the infection is downloaded from a remote location and started on the local machine.

Another popular tactic for spreading malware is the creation of hacker-controlled sites. They may pose as legitimate download sites, search engines or vendors and attempt to deliver the virus file. A large part of them actually contain malware software installers. They represent modified setup files taken from the official vendors. The hacker operators behind the .Black_OFFserve virus hijack them and include the malware component. The resulting installer is then uploaded to the relevant hacker-operated site.

The hacker-controlled sites can also be found via browser hijacker instances. Users can get redirected to the via ads, scripts and banners placed on other sites or through a browser hijacker. They are malware extensions made for the most popular web browsers. Usually the list includes the following applications: Mozilla Firefox, Google Chrome, Safari, Microsoft Edge, Opera and Internet Explorer. Their standard behavior patterns are to redirect the victims to the hacker-controlled download page or directly deliver the infection automatically. They are especially dangerous as they can be further modified to cause other system changes as well.

RotorCrypt Ransomware – In-Depth Description

The RotorCrypt ransomware has been spotted in a new attack campaign. The new strain uses the .Black_OFFserve extension to differentiate itself from prior samples. Like all updated versions it is a customized variant of the original code and as such follows the same behavior patterns.

After infection the samples do not immediately begin to alter the system but delay the virus execution. This is part of the malware family’s stealth protection mechanism. It delays the virus infection on purposes in order to evade any signature and behavior scans that may be running. Another strategy that can be employed can also scan the system for any running security software (anti-virus products, sandbox and debug environments, as well as virtual machines). If found their real-time engines can be disabled or completely removed. Depending on the hacker configuration the virus may delete itself to avoid detection.

One this is done the malware engine hooks itself to system processes and hides itself in the Microsoft Windows system folder as a legitimate component. The security experts have been able to identify several prior attack campaigns that hide their tracks from the system itself as well.

If the samples associated with the .Black_OFFserve extension are direct derivatives they can suppress the error messages that are the result of its execution. The next step in the behavior pattern is the detailed information gathering process. It aims to extract two main types of data that is directly sent to the hacker operators:

  • Anonymous Metrics — This type of information refers to system information that is collected for statistical purposes by the hackers. Example data usually includes operating system version and date and time of the infections.
  • Personally-identifiable Data — The malware engine can extract information that can directly expose the users identity. This may include their names, address, preferences, interests and etc.

System changes can also impact the Windows Registry by manipulating existing values or creating new ones. This step may be part of the persistent state of execution which is achieved. It allows the malware instance to automatically block manual user removal attempts by constantly monitoring their behavior. It can also interact with the Windows volume manager which allows the ransomware component to affect files located on remoovable storage devices and available network shares as well.

Such infections can be bundled alongside Trojan code which allows the hackers to spy on the victims in real time as well as take over control of their machines at any given time.

An additional danger is the fact that the RotorCrypt ransomware samples can retrieve all data files prior to the encryption phase. This is especially useful when the hackers attempt blackmail strategies upon the victims.

The malware component also deletes all found Shadow Volume copies which makes it more difficult for the users to restore their files. In these cases a professional data recovery solution needs to be used as well.

RotorCrypt Ransomware – Encryption Process

Once all infections have complete the ransomware component is started. It is able to encrypt user files according to a built-in list of target file type extensions.

A sample list retrieved from earlier versions targets the following data:

.1cd, .avi, .bak, .bmp, .cf, .cfu, .csv, .db, .dbf, .djvu, .doc, .docx, .dt, .elf, .epf, .erf, .exe,
.flv, .geo, .gif, .grs, .jpeg, .jpg, .lgf, .lgp, .log, .mb, .mdb, .mdf, .mxl, .net, .odt, .pdf, .png,
.pps, .ppt, .pptm, .pptx, .psd, .px, .rar, .raw, .st, .sql, .tif, .txt, .vob, .vrp, .xls, .xlsb, .xlsx,
.xml, .zip

A notable addition to the file type extensions are several extensions that are used against book keeping and business software. It is very likely that the criminal operators initiate attacks against such victims.

Depending on the exact campaign that victims can receive different ransomware notes. They are frequently tweaked according to the victim users. A generic message retrieved from one of the samples reads the following:

Good day
Your files were encrypted/locked
As evidence can decrypt file 1 to 3 1-30MB
The price of the transcripts of all the files on the server: 7 Bitcoin
Recommend to solve the problem quickly and not to delay
Also give advice on how to protect Your server against threats from the network
(Files sql mdf backup decryption strictly after payment)!

The current active campaign assigns the following extension to the victim files: !==SOLUTION OF THE [email protected]==.Black_OFFserve.

Previous Rotorcrypt ransomware attacks were found to feature these renaming schemes:

Remove RotorCrypt Ransomware and Restore .Black_OFFserve Files

If your computer got infected with the RotorCrypt ransomware virus, you should have a bit of experience in removing malware. You should get rid of this ransomware as quickly as possible before it can have the chance to spread further and infect other computers. You should remove the ransomware and follow the step-by-step instructions guide provided below.

Martin Beltov

Martin graduated with a degree in Publishing from Sofia University. As a cyber security enthusiast he enjoys writing about the latest threats and mechanisms of intrusion.

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