Cesar (.cesar) ransomware virus - removal and decryption options
Written by Tomas Meskauskas on (updated)
What kind of malware is Cesar ransomware?
Cesar is the name of a malicious program belonging to the Dharma ransomware group. Systems infected with this malware - have their data encrypted (files rendered inaccessible) and receive ransom demands for the decryption (access recovery).
During the encryption process, affected files are renamed following this pattern: original filename, unique ID assigned to the victims, cyber criminals' email address, and ".cesar" extension. For example, a file initially titled "1.jpg" would appear as something similar to "1.jpg.id-C279F237.[yasomoto@tutanota.com].cesar" - after encryption.
Once this process is complete, ransom-demanding messages are created/displayed in a pop-up window and "FILES ENCRYPTED.txt" text file.
Screenshot of files encrypted by Cesar (".cesar" extension):
Ransom note overview
The text presented in "FILES ENCRYPTED.txt" informs victims that their data has been locked. The note instructs writing to the listed email addresses - to recover the compromised files.
The ransom note in the pop-up window provides more information concerning the ransomware infection. It clarifies that the files have been encrypted and states that victims will have to pay - to decrypt them.
The message does not specify the size of the ransom, but it does inform victims that it will have to be paid in Bitcoin cryptocurrency. To get further instructions, contact has to be established with the cyber criminals via email.
The title/subject of the email letters must be the ID assigned to victims (present in the pop-up window and modified filenames). Should no reply from the criminals arrive after 24 hours, the note contains a secondary email address.
Free decryption of five files is offered as proof that recovery is possible. The test files will be decrypted and sent back if they meet these criteria - the total size of the files does not exceed 10MB (non-archived), and they do not contain valuable information (e.g., databases, backups, large Excel sheets, etc.).
The message is concluded with warnings. Victims are alerted that renaming the encrypted files and/or trying to decrypt them will third-party tools/software - may result in permanent data loss.
More about ransomware
Unfortunately, in most ransomware attacks, without the cyber criminals' interference - decryption is impossible. It might be if the malicious program is still in development and/or has serious bugs (flaws). Whatever the case, it is strongly advised against communicating with and paying criminals. Often, despite meeting the ransom demands - victims do not receive the decryption tools/software.
Therefore, they experience financial loss and their data remains locked and useless. Removing Cesar ransomware from the operating system will prevent it from encrypting more files.
However, removal will not restore already affected data. The only solution is recovering the files from a backup, if one was made before the infection and stored in a different location.
Similarities between ransomware attacks
Eye, Igvm, and CALVO are a couple examples of malicious programs within the ransomware classification. This malware is designed to encrypt data and/or lock the device's screen - in order to demand payment for the decryption/ access recovery.
There are two significant differences in-between ransomware - the cryptographic algorithms it uses (symmetric or asymmetric) and the ransom size.
Digital currencies (primarily cryptocurrencies) are used because their transactions are difficult/impossible to trace. Hence, it complicates the cyber criminals' persecution and prevents victims from returning their money.
To protect data, it is highly recommended to keep backups in remote servers and/or unplugged storage devices. Ideally, backup copies should be stored in multiple separate locations.
How did ransomware infect my computer?
Ransomware and other malware are distributed using a wide variety of techniques and tactics. Malicious programs are often disguised as or packed together with ordinary software/media.
Untrustworthy download channels (e.g., unofficial and free file-hosting websites, Peer-to-Peer sharing networks, and other third-party downloaders) are used to spread malware. Illegal activation tools ("cracks") and fake updates are prime examples of content employed to proliferate malicious software.
"Cracking" tools can infect systems instead of activating licensed products. Fraudulent updaters cause infections by abusing flaws of outdated programs and/or by installing malicious software rather than the promised updates.
Malware is also commonly distributed via spam campaigns. This term defines a mass-scale operation during which deceptive/scam emails are sent by the thousand.
These letters are usually presented as "urgent", "important", "priority", and/or as mail from legitimate companies, organizations, institutions, and other entities. The emails have infectious files attached to or linked inside them.
Virulent files can be in various formats, e.g., Microsoft Office and PDF documents, archives (ZIP, RAR, etc.), executables (.exe, .run, etc.), JavaScript, and so forth. When the files are opened - the infection process is initiated.
| Name | Cesar virus |
| Threat Type | Ransomware, Crypto Virus, Files locker |
| Encrypted Files Extension | .cesar (files are also appended with unique ID and cyber criminals' email address) |
| Ransom Demanding Message | Text presented in the pop-up window and FILES ENCRYPTED.txt |
| Cyber Criminal Contact | invisibilia_homo@aol.com, macgregor@aolonline.top, yasomoto@tutanota.com and yasomoto@cock.li |
| Detection Names | Avast (Win32:Malware-gen), BitDefender (Trojan.Ransom.Crysis.E), ESET-NOD32 (A Variant Of Win32/Filecoder.Crysis.P), Kaspersky (Trojan-Ransom.Win32.Crusis.to), Microsoft (Ransom:Win32/Wadhrama), Full List Of Detections (VirusTotal) |
| Symptoms | Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files. |
| Distribution methods | Infected email attachments (macros), torrent websites, malicious ads. |
| Damage | All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection. |
| Malware Removal (Windows) | To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner. |
How to protect yourself from ransomware infections?
It is important to always download from official and verified sources. Furthermore, all programs must be activated and updated using tools/functions provided by genuine developers.
To avoid infecting the system via spam mail, it is advised against opening dubious and irrelevant emails - especially any attachments or links present in them. It is paramount to have a dependable anti-virus/anti-spyware suite installed.
This software must be kept updated, used to perform regular system scans and remove detected/potential threats. If your computer is already infected with Cesar, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.
Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:
Text presented in Cesar ransomware's pop-up window:
All your files have been encrypted!
All your files have been encrypted due to a security problem with your PC. If you want to restore them, write us to the e-mail yasomoto@tutanota.com
Write this ID in the title of your message -
In case of no answer in 24 hours write us to theese e-mails:yasomoto@cock.li
You have to pay for decryption in Bitcoins. The price depends on how fast you write to us. After payment we will send you the decryption tool that will decrypt all your files.
Free decryption as guarantee
Before paying you can send us up to 5 files for free decryption. The total size of files must be less than 10Mb (non archived), and files should not contain valuable information. (databases,backups, large excel sheets, etc.)
How to obtain Bitcoins
The easiest way to buy bitcoins is LocalBitcoins site. You have to register, click 'Buy bitcoins', and select the seller by payment method and price.
hxxps://localbitcoins.com/buy_bitcoins
Also you can find other places to buy Bitcoins and beginners guide here:
hxxp://www.coindesk.com/information/how-can-i-buy-bitcoins/
Attention!
Do not rename encrypted files.
Do not try to decrypt your data using third party software, it may cause permanent data loss.
Decryption of your files with the help of third parties may cause increased price (they add their fee to our) or you can become a victim of a scam.
Screenshot of Cesar's text file ("FILES ENCRYPTED.txt"):
Text presented in this file:
all your data has been locked us
You want to return?
write email yasomoto@tutanota.com or yasomoto@cock.li
Cesar ransomware removal:
Instant automatic malware removal:
Manual threat removal might be a lengthy and complicated process that requires advanced IT skills. Combo Cleaner is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
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Video suggesting what steps should be taken in case of a ransomware infection:
Quick menu:
- What is Cesar virus?
- STEP 1. Reporting ransomware to authorities.
- STEP 2. Isolating the infected device.
- STEP 3. Identifying the ransomware infection.
- STEP 4. Searching for ransomware decryption tools.
- STEP 5. Restoring files with data recovery tools.
- STEP 6. Creating data backups.
If you are a victim of a ransomware attack we recommend reporting this incident to authorities. By providing information to law enforcement agencies you will help track cybercrime and potentially assist in the prosecution of the attackers. Here's a list of authorities where you should report a ransomware attack. For the complete list of local cybersecurity centers and information on why you should report ransomware attacks, read this article.
List of local authorities where ransomware attacks should be reported (choose one depending on your residence address):
USA - Internet Crime Complaint Centre IC3
United Kingdom - Action Fraud
Spain - Policía Nacional
France - Ministère de l'Intérieur
Germany - Polizei
Italy - Polizia di Stato
The Netherlands - Politie
Poland - Policja
Portugal - Polícia Judiciária
Isolating the infected device:
Some ransomware-type infections are designed to encrypt files within external storage devices, infect them, and even spread throughout the entire local network. For this reason, it is very important to isolate the infected device (computer) as soon as possible.
Step 1: Disconnect from the internet.
The easiest way to disconnect a computer from the internet is to unplug the Ethernet cable from the motherboard, however, some devices are connected via a wireless network and for some users (especially those who are not particularly tech-savvy), disconnecting cables may seem troublesome. Therefore, you can also disconnect the system manually via Control Panel:
Navigate to the "Control Panel", click the search bar in the upper-right corner of the screen, enter "Network and Sharing Center" and select search result: 
Click the "Change adapter settings" option in the upper-left corner of the window: 
Right-click on each connection point and select "Disable". Once disabled, the system will no longer be connected to the internet. To re-enable the connection points, simply right-click again and select "Enable". 
Step 2: Unplug all storage devices.
As mentioned above, ransomware might encrypt data and infiltrate all storage devices that are connected to the computer. For this reason, all external storage devices (flash drives, portable hard drives, etc.) should be disconnected immediately, however, we strongly advise you to eject each device before disconnecting to prevent data corruption:
Navigate to "My Computer", right-click on each connected device, and select "Eject": 
Step 3: Log-out of cloud storage accounts.
Some ransomware-type might be able to hijack software that handles data stored within "the Cloud". Therefore, the data could be corrupted/encrypted. For this reason, you should log-out of all cloud storage accounts within browsers and other related software. You should also consider temporarily uninstalling the cloud-management software until the infection is completely removed.
Identify the ransomware infection:
To properly handle an infection, one must first identify it. Some ransomware infections use ransom-demand messages as an introduction (see the WALDO ransomware text file below).
This, however, is rare. In most cases, ransomware infections deliver more direct messages simply stating that data is encrypted and that victims must pay some sort of ransom. Note that ransomware-type infections typically generate messages with different file names (for example, "_readme.txt", "READ-ME.txt", "DECRYPTION_INSTRUCTIONS.txt", "DECRYPT_FILES.html", etc.). Therefore, using the name of a ransom message may seem like a good way to identify the infection. The problem is that most of these names are generic and some infections use the same names, even though the delivered messages are different and the infections themselves are unrelated. Therefore, using the message filename alone can be ineffective and even lead to permanent data loss (for example, by attempting to decrypt data using tools designed for different ransomware infections, users are likely to end up permanently damaging files and decryption will no longer be possible even with the correct tool).
Another way to identify a ransomware infection is to check the file extension, which is appended to each encrypted file. Ransomware infections are often named by the extensions they append (see files encrypted by Qewe ransomware below).
This method is only effective, however, when the appended extension is unique - many ransomware infections append a generic extension (for example, ".encrypted", ".enc", ".crypted", ".locked", etc.). In these cases, identifying ransomware by its appended extension becomes impossible.
One of the easiest and quickest ways to identify a ransomware infection is to use the ID Ransomware website. This service supports most existing ransomware infections. Victims simply upload a ransom message and/or one encrypted file (we advise you to upload both if possible).
The ransomware will be identified within seconds and you will be provided with various details, such as the name of the malware family to which the infection belongs, whether it is decryptable, and so on.
Example 1 (Qewe [Stop/Djvu] ransomware):
Example 2 (.iso [Phobos] ransomware):
If your data happens to be encrypted by ransomware that is not supported by ID Ransomware, you can always try searching the internet by using certain keywords (for example, a ransom message title, file extension, provided contact emails, crypto wallet addresses, etc.).
Search for ransomware decryption tools:
Encryption algorithms used by most ransomware-type infections are extremely sophisticated and, if the encryption is performed properly, only the developer is capable of restoring data. This is because decryption requires a specific key, which is generated during the encryption. Restoring data without the key is impossible. In most cases, cybercriminals store keys on a remote server, rather than using the infected machine as a host. Dharma (CrySis), Phobos, and other families of high-end ransomware infections are virtually flawless, and thus restoring data encrypted without the developers' involvement is simply impossible. Despite this, there are dozens of ransomware-type infections that are poorly developed and contain a number of flaws (for example, the use of identical encryption/decryption keys for each victim, keys stored locally, etc.). Therefore, always check for available decryption tools for any ransomware that infiltrates your computer.
Finding the correct decryption tool on the internet can be very frustrating. For this reason, we recommend that you use the No More Ransom Project and this is where identifying the ransomware infection is useful. The No More Ransom Project website contains a "Decryption Tools" section with a search bar. Enter the name of the identified ransomware, and all available decryptors (if there are any) will be listed.
Restore files with data recovery tools:
Depending on the situation (quality of ransomware infection, type of encryption algorithm used, etc.), restoring data with certain third-party tools might be possible. Therefore, we advise you to use the Recuva tool developed by CCleaner. This tool supports over a thousand data types (graphics, video, audio, documents, etc.) and it is very intuitive (little knowledge is necessary to recover data). In addition, the recovery feature is completely free.
Step 1: Perform a scan.
Run the Recuva application and follow the wizard. You will be prompted with several windows allowing you to choose what file types to look for, which locations should be scanned, etc. All you need to do is select the options you're looking for and start the scan. We advise you to enable the "Deep Scan" before starting, otherwise, the application's scanning capabilities will be restricted.
Wait for Recuva to complete the scan. The scanning duration depends on the volume of files (both in quantity and size) that you are scanning (for example, several hundred gigabytes could take over an hour to scan). Therefore, be patient during the scanning process. We also advise against modifying or deleting existing files, since this might interfere with the scan. If you add additional data (for example, downloading files/content) while scanning, this will prolong the process:
Step 2: Recover data.
Once the process is complete, select the folders/files you wish to restore and simply click "Recover". Note that some free space on your storage drive is necessary to restore data:
Create data backups:
Proper file management and creating backups is essential for data security. Therefore, always be very careful and think ahead.
Partition management: We recommend that you store your data in multiple partitions and avoid storing important files within the partition that contains the entire operating system. If you fall into a situation whereby you cannot boot the system and are forced to format the disk on which the operating system is installed (in most cases, this is where malware infections hide), you will lose all data stored within that drive. This is the advantage of having multiple partitions: if you have the entire storage device assigned to a single partition, you will be forced to delete everything, however, creating multiple partitions and allocating the data properly allows you to prevent such problems. You can easily format a single partition without affecting the others - therefore, one will be cleaned and the others will remain untouched, and your data will be saved. Managing partitions is quite simple and you can find all the necessary information on Microsoft's documentation web page.
Data backups: One of the most reliable backup methods is to use an external storage device and keep it unplugged. Copy your data to an external hard drive, flash (thumb) drive, SSD, HDD, or any other storage device, unplug it and store it in a dry place away from the sun and extreme temperatures. This method is, however, quite inefficient, since data backups and updates need to be made regularly. You can also use a cloud service or remote server. Here, an internet connection is required and there is always the chance of a security breach, although it's a really rare occasion.
We recommend using Microsoft OneDrive for backing up your files. OneDrive lets you store your personal files and data in the cloud, sync files across computers and mobile devices, allowing you to access and edit your files from all of your Windows devices. OneDrive lets you save, share and preview files, access download history, move, delete, and rename files, as well as create new folders, and much more.
You can back up your most important folders and files on your PC (your Desktop, Documents, and Pictures folders). Some of OneDrive’s more notable features include file versioning, which keeps older versions of files for up to 30 days. OneDrive features a recycling bin in which all of your deleted files are stored for a limited time. Deleted files are not counted as part of the user’s allocation.
The service is built using HTML5 technologies and allows you to upload files up to 300 MB via drag and drop into the web browser or up to 10 GB via the OneDrive desktop application. With OneDrive, you can download entire folders as a single ZIP file with up to 10,000 files, although it can’t exceed 15 GB per single download.
OneDrive comes with 5 GB of free storage out of the box, with an additional 100 GB, 1 TB, and 6 TB storage options available for a subscription-based fee. You can get one of these storage plans by either purchasing additional storage separately or with Office 365 subscription.
Creating a data backup:
The backup process is the same for all file types and folders. Here’s how you can back up your files using Microsoft OneDrive
Step 1: Choose the files/folders you want to backup.
Click the OneDrive cloud icon to open the OneDrive menu. While in this menu, you can customize your file backup settings.
Click Help & Settings and then select Settings from the drop-down menu.
Go to the Backup tab and click Manage backup.
In this menu, you can choose to backup the Desktop and all of the files on it, and Documents and Pictures folders, again, with all of the files in them. Click Start backup.
Now, when you add a file or folder in the Desktop and Documents and Pictures folders, they will be automatically backed up on OneDrive.
To add folders and files, not in the locations shown above, you have to add them manually.
Open File Explorer and navigate to the location of the folder/file you want to backup. Select the item, right-click it, and click Copy.
Then, navigate to OneDrive, right-click anywhere in the window and click Paste. Alternatively, you can just drag and drop a file into OneDrive. OneDrive will automatically create a backup of the folder/file.
All of the files added to the OneDrive folder are backed up in the cloud automatically. The green circle with the checkmark in it indicates that the file is available both locally and on OneDrive and that the file version is the same on both. The blue cloud icon indicates that the file has not been synced and is available only on OneDrive. The sync icon indicates that the file is currently syncing.
To access files only located on OneDrive online, go to the Help & Settings drop-down menu and select View online.
Step 2: Restore corrupted files.
OneDrive makes sure that the files stay in sync, so the version of the file on the computer is the same version on the cloud. However, if ransomware has encrypted your files, you can take advantage of OneDrive’s Version history feature that will allow you to restore the file versions prior to encryption.
Microsoft 365 has a ransomware detection feature that notifies you when your OneDrive files have been attacked and guide you through the process of restoring your files. It must be noted, however, that if you don’t have a paid Microsoft 365 subscription, you only get one detection and file recovery for free.
If your OneDrive files get deleted, corrupted, or infected by malware, you can restore your entire OneDrive to a previous state. Here’s how you can restore your entire OneDrive:
1. If you're signed in with a personal account, click the Settings cog at the top of the page. Then, click Options and select Restore your OneDrive.
If you're signed in with a work or school account, click the Settings cog at the top of the page. Then, click Restore your OneDrive.
2. On the Restore your OneDrive page, select a date from the drop-down list. Note that if you're restoring your files after automatic ransomware detection, a restore date will be selected for you.
3. After configuring all of the file restoration options, click Restore to undo all the activities you selected.
The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups.
Frequently Asked Questions (FAQ)
How was my computer hacked and how did hackers encrypt my files?
Ransomware can infiltrate computers through diverse methods, including malicious spam emails, malicious ads, and drive-by downloads. Cybercriminals frequently conceal ransomware executables within cracked software distribution websites, deceiving users into unwittingly downloading and running malware on their systems.
How to open ".cesar" files?
Your files have been encrypted due to a ransomware infection. In order to access and use your files, decryption is necessary.
Where should I look for free decryption tools for Cesar ransomware?
In case of a ransomware attack you should check the No More Ransom project website (more information above).
I can pay you a lot of money, can you decrypt files for me?
Unfortunately, we are unable to offer this service. Decrypting files encrypted by ransomware is usually only feasible with the involvement of cybercriminals unless the ransomware has inherent vulnerabilities. Therefore, if third parties offer paid decryption services, they might act as intermediaries or try to scam you.
Will Combo Cleaner help me remove Cesar ransomware?
Combo Cleaner is designed to scan your computer and remove active ransomware infections. However, it is important to understand that while utilizing an antivirus program is an initial step in addressing ransomware, security software does not possess the capability to decrypt encrypted files.
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