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Cesar ransomware virus: how to decrypt .cesar files

6 min read
This article provides comprehensive details of the new Crysis / Dharma ransomware variant that appends the .cesar or .cezar extension to encrypted files.

The Crysis ransomware, previously known as Dharma, has suddenly awoken after several months of inactivity. Moreover, the halt was accompanied by an anonymous dump of master decryption keys in late May 2017. Although events like that tend to denote that a campaign stops for good, somebody in the cybercriminal underground must have a different opinion, obviously. The latest outbreak of the Crysis / Dharma ransomware wave revolves around a variant that blemishes one’s encoded files with the .cesar extension. Some of the more recent reports have unveiled the .cezar file version as well. This string is only part of the concatenated extension, though. It is preceded by a victim’s ID and the threat actors’ contact email address so that the infected user gets quite a few clues on data decryption from the get-go.

Cesar ransomware Info.hta rescue note

The upshot of this data tweaking workflow is that an arbitrary filename gets concatenated with an extension token in the following format: .id-{8-char victim ID}.[email address].cesar. For example, a sample item named Coffee.jpg will morph into something like Coffee.jpg.id-C21FD978.[m.heisenberg@aol.com].cesar. Note that the email part may vary. Aside from the one mentioned above, it can be black.mirror@qq.com, gladius_rectus@aol.com, or btc2017@india.com. The email address variable most likely denotes a specific ‘affiliate’ that was able to deposit the perpetrating code onto a computer. There are different groups of cybercrooks distributing the Cesar ransomware edition of Crysis concurrently, each one with their own contacts.

As opposed to most file-encrypting strains out there that spread by means of malicious spam, the Cesar virus is making the rounds via Remote Desktop Protocol. The attackers brute-force RDP credentials in order to infiltrate systems remotely. This way, they can execute random code on compromised computers. In the case of Cesar, the troublemaking process is named bars.exe. When deployed inside a machine, this executable deletes Shadow Copies of the victim’s files and adds a registry value to run when the OS is booted up. Then, the ransomware scans the local drive and removable drives, if any, for a predefined list of data formats. It encrypts every single file detected during this scan.

Whereas the extension affixed to all hostage files is quite self-explanatory in terms of what the user should do, the Cesar virus also drops a ransom note named Info.hta onto the desktop. According to this note, the victim has to send a message to the email address indicated in square brackets preceding the .cesar part of the file extension. The plagued user is instructed to include their personal ID in this email. The felons will respond with the size of the ransom and the Bitcoin wallet address to submit it. As guarantee that the decryption tool will work, the extortionists can purportedly restore up to three files whose total size doesn’t exceed 10 MB. All in all, instead of relying on the bad guys’ promises and going through the painful buyout procedure, start with alternative data restoration options below.

Cesar ransomware automated removal and data recovery

The battle-tested security tool called WiperSoft can shore up the protection of your PC by identifying and removing all files associated with Cesar threat automatically. It gets regular updates of its malware database to ensure a high detection rate, even if you’ve been hit by the newest strain of ransomware, adware, spyware, or a stubborn browser hijacker.

The following point-by-point instructions will help you get your computer back on track using this incredibly effective application.

1. Download the latest version of WiperSoft.

WiperSoft scans your PC with no strings attached, but you’ll have to register its commercial version to immediately remove the threats it detects. Alternatively, you can use a one-time free cleaning service that will activate in 48 hours after you opt for it.

Download Cesar ransomware remover

2. Run the installer. As part of the setup, you’ll be asked to specify your preferred language and accept the End User License Agreement.WiperSoft installation progress

3. Once the installation is through, you’ll see the app’s Home screen that says, “Computer state is unknown”. Click Scan Now to check your system for threats.Start a scan

4. The first scan might take a while to be completed. This is normal, given that the app has to check hundreds of thousands of files along the way. It will reflect the current progress and other details at the bottom part of the GUI.WiperSoft scan progress

5. If WiperSoft finds malicious files, it will let you know via an updated computer security status as illustrated below. Go ahead and click the Review & Clean button.‘Malicious items were found’ alert

6. Go over the detailed scan report that’s split into three categories: malware, potentially unwanted programs (PUPs), and privacy issues. Make sure all unwanted items are selected and click Remove Threats to disinfect your PC.Remove detected threats

Data recovery toolkit to the rescue

Some strains of ransomware are known to delete the original files after the encryption routine has been completed. As hostile as this activity appears, it can play into your hands. There are applications designed to revive the information that was obliterated because of malfunctioning hardware or due to accidental removal. The tool called Stellar Data Recovery features this type of a capability and therefore it can be applied in ransom attack scenarios to at least get the most important files back. So use the app to get an idea of what data can be restored and let it do the recovery job. Here is a step-by-step walkthrough:

1. Download and install Stellar Data Recovery.

Download Stellar Data Recovery

2. Open the application, select the types of recoverable files to look for, and click Next.Stellar Data Recovery main screen

3. Choose the areas you want the tool to recover from and click the Scan button.Select which PC areas to recover from

4. Having scanned the specified locations, the program will display a notification about the total amount of recoverable data. Close the dialog and click the Recover button. This will hopefully help you get some of your valuable files back.Recover files

Cesar ransomware manual removal and file recovery

Some ransomware strains terminate themselves after completing the encryption job on a computer, but some don’t. Furthermore, the Cesar virus may prevent victims from using popular antimalware tools in order to stay on board for as long as possible. Under the circumstances, it may be necessary to utilize the Safe Mode with Networking or System Restore functionality.

Remove Cesar ransomware using Safe Mode with Networking

Remove Cesar ransomware using Safe Mode with Networking

Get rid of Cesar ransomware using System Restore

Get rid of Cesar ransomware using System Restore

System Restore enables Windows users to roll back all changes made to the OS since the latest restore point creation time. This feature can help eliminate the most persistent ransomware. Before going this route, though, make sure System Restore had been enabled prior to the breach, otherwise the method will be inefficient.

  • Open Windows Advanced Options Menu as described in the previous section: hit F8 repeatedly when the PC is starting up. Use arrow keys to highlight the Safe Mode with Command Prompt entry. Hit Enter.Safe Mode with Command Prompt
  • In the Command Prompt window, type cd restore and hit Entercd restore command
  • Type rstrui.exe in the new command line and press EnterType rstrui.exe command
  • When the System Restore screen pops up, click Next, select a restore point that predates the contamination, and use the application’s controls to roll back the system to this earlier state.System Restore window
Be advised that even after the ransomware is removed, files will still be encrypted and inaccessible. The malicious code cleanup part, however, is important because it keeps a relapse of the infection from occurring further on and eliminates all opportunistic malware.

Cracking the crypto used by this ransom Trojan is more of a science fiction thing rather than an attainable prospect for the masses. This is why the troubleshooting in predicaments of this sort is a matter of two approaches: one is to pay the ransom, which isn’t an option for many victims; and the other is to apply instruments that take advantage of the ransomware’s possible weaknesses. If the latter is your pick, the advice below is a must-try.

Backups can make your day

Backups can make your day

Not only are you a lucky person in case you’ve been backing up your most important files, but you’re also a wise and prudent user. This isn’t necessarily a resource-heavy activity these days – in fact, some providers of online services are allocating a sufficient size of cloud storage space for free so that every customer can easily upload their critical data without paying a penny. Having removed the Cesar ransomware, therefore, all you have to do is download your stuff from the remote server or transfer it all from an external piece of hardware if that’s the case.

Restore previous versions of encrypted files

Restore previous versions of encrypted files

A positive upshot of using this technique depends on whether or not the ransomware has erased the Volume Shadow Copies of the files on your PC. This is a Windows feature that automatically makes and keeps the backups of data elements on the hard drive as long as System Restore is enabled. The cryptoware in question is programmed to switch off the Volume Shadow Copy Service (VSS), but it has reportedly failed to in some cases.

Checking one’s options regarding this workaround is doable in two ways: through the Properties menu of each file or by means of the remarkable open-source tool called Shadow Explorer. We recommend the software-based way because it’s automated, hence faster and easier. Just install the app and use its intuitive controls to get previous versions of the encrypted objects reinstated.

Shadow Explorer

Alternatively, you can leverage the Previous Versions feature, which is native to Windows operating system. This method is more cumbersome that the use of ShadowExplorer, but it can help restore the most important individual files on condition that the ransomware failed to disable the Volume Snapshot Service on the computer. Right-click on a file of choice and select Properties. Then, go to the Previous Versions tab as illustrated below.

Previous Versions

Go ahead and pick the file’s latest backup version on the list. Use the Copy or Restore buttons to reinstate this object to a new path or to its original folder, respectively.

Ransomware Prevention Tips

To avoid Cesar ransomware and other file-encrypting infections in the future, follow several simple recommendations:

  • Toggle your email provider’s anti-spam settings to filter out all the potentially harmful incoming messages. Raising the bar beyond the default protection is an important countermeasure for ransom Trojans
  • Define specific file extension restrictions in your email system. Make sure that attachments with the following extensions are blacklisted: .js
  • .vbs
  • .docm
  • .hta
  • .exe
  • .cmd
  • .scr
  • and .bat. Also
  • treat ZIP archives in received messages with extreme caution
  • Rename the vssadmin.exe process so that ransomware is unable to obliterate all Shadow Volume Copies of your files in one shot
  • Keep your Firewall active at all times. It can prevent crypto ransomware from communicating with its C&C server. This way
  • the threat won’t be able to obtain cryptographic keys and lock your files
  • Back up your files regularly
  • at least the most important ones. This recommendation is self-explanatory. A ransomware attack isn’t an issue as long as you keep unaffected copies of your data in a safe place
  • Use an effective antimalware suite. There are security tools that identify ransomware-specific behavior and block the infection before it can do any harm.

These techniques are certainly not a cure-all, but they will add an extra layer of ransomware protection to your security setup.

Revise your security status

Post-factum assessment of the accuracy component in malware removal scenarios is a great habit that prevents the comeback of harmful code or replication of its unattended fractions. Make sure you are good to go by running an additional safety checkup. Another benefit of using the antimalware tool is that it will keep ransomware threats from intruding on your computer further on.

Download Cesar ransomware removal tool

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