Geek's Advice

EFDC ransomware uses robust encryption to lock files on victim’s computer

EFDC ransomware is a malicious file-encrypting computer virus that is part of STOP/DJVU malware group. Once executed on the target system, it scans all directories and encrypts all files using RSA Salsa20 algorithm, thus marking each file with an additional .efdc extension. Consequently, a file originally named 1.jpg becomes 1.jpg.efdc after being modified. The virus is also set to drop a ransom note called _readme.txt in every data folder. This note explains that the virus has compromised victim’s computer, thus locking all files found on it, and the only possible way of obtaining EFDC decryption tool is paying a ransom for virus’ developers. According to the note, the decryption price relies on how quickly the victim writes to attackers via provided emails – helpmanager@airmail.cc or manager@mailtemp.ch. If the victim manages to settle an agreement and pay within 72 hours, criminals suggest a 50% discount which results in $490 for the tool and decryption key. Otherwise, the victim needs to pay a full amount, which is $980.

EFDC ransomware virus is designed to temporarily lock victim’s files using encryption algorithms. Encryption is usually used to secure information so that only the person who has the decryption key could access it. In this case, the criminals have it, and they try to extort the computer user by keeping one’s files hostage and demanding to pay an enormous ransom.

The way this virus works is that it encrypts the first 150KB of each file, which is enough to render the file useless yet also keep the entire computer attack procedure speedy. However, due to the fact that the ransomware only corrupts a portion of a file, certain data formats can be repaired as explained in this self-help guide.

The ransom note left on victim’s desktop and every single folder with encrypted files explain what happened and suggests contacting the criminals via two provided email addresses. As stated in _readme.txt file, the criminals are willing to give the victim a 50% discount if one puts the effort to contact the criminals within 72 hours. However, we believe that the victim is also expected to make the transaction in the same time period, which might be hard because the attackers will only accept the payment in cryptocurrency (such as Bitcoin). That said, the EFDC decryption tool price would be $490 in 3 days or $980 later. The ransom note also suggests that the victim can test the decryption by attaching a small encrypted file to the email for the criminals.

However, our team members as well as cybersecurity experts worldwide will confirm that paying a ransom might be a really bad idea. In fact, FBI confirms it as well. Here are a couple of arguments against ransom payments:

• Remember that paying a ransom does not guarantee file recovery.
• Ransomware gangs earn millions of US dollars each year. The large amount of money they get by extorting computer users attracts other people to join distribution of such malware. Please, do not contribute to the growth of this!
• Paying a ransom is considered an illegal act in certain countries.
• Viruses from STOP/DJVU ransomware family such as EFDC often carry AZORULT Trojan alongside them and drop it on compromised computers. It is malware that steals private information that can be used for further blackmail.

REMOVE MALWARE & REPAIR VIRUS DAMAGE

How this ransomware works

Once on the target system, EFDC ransomware first performs some checks such as whether Internet connection is on or not. It is required for the virus to connect to its Command&Control server and get the encryption key for the victim. The virus also saves it in a text file on victim’s computer as well as victim’s personal ID. If there is no connection, the ransomware uses a hardcoded offline key (ending in t1) instead.

The virus then runs a fake Windows update prompt on the screen in order to deceive the victim and justify the sudden system slowdown. Now the virus starts the encryption procedure and marks each file with a new extension, plus leaves _readme.txt notes in every computer folder. The ransomware also uses a Command Line task to delete Volume Shadow Copies from the system:

^{vssadmin.exe Delete Shadows /All /Quiet}

Once Shadow Copies are removed, the victim loses one’s chances to recover part of the data using System Restore Points. Next thing this virus does is to add a list of domains to Windows HOSTS file, which can be used to map domain names to host IPs. In this scenario, the virus maps a list of computer or cybersecurity-related sites to victim’s localhost IP, which later results in a failure if the victim attempts to open one of these sites using a web browser. Most of the time, the victim will see DNS_PROBE_FINISHED_NXDOMAIN error due to DNS resolution problem caused by the ransomware.

However, probably the worst part (despite data encryption) is that EFDC ransomware virus drops information-stealing Trojan, namely AZORULT on the computer as well. Unfortunately, the crooks do not mention a single word about it in the ransom note they leave behind. This Trojan is categorized as one who can be used by criminals to remotely access victim’s computer and use various command-line tasks to perform illegal activities on victim’s computer, such as:

• Download various computer malware and running it;
• Take various login credentials, such as those of Telegram, Steam and other programs and send them to criminals;
• View or delete files on the victim’s computer;
• Steal cryptocurrency wallets and their contents;
• Steal browser-saved passwords, browser cookies, browsing history and more.

We believe there is no need to get into other technical details since it is apparent that this ransomware is highly dangerous, plus its activities make your computer vulnerable to further cyber attacks. The best idea right now is to take action to remove EFDC ransomware virus from your Windows computer, ideally, with a professional antivirus program such as INTEGO Antivirus, which we highly recommend. It can provide real-time protection and stop you from entering various phishing or dangerous Internet sites. Moreover, we also recommend scanning with RESTORO to repair virus damage to your Windows OS files.

Ransomware Summary

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Ransomware distribution explained

Ransomware-type computer viruses are distributed in several ways, although they all can be called traditional malware distribution ways whatsoever. For example, one of the most popular ways to spread any kind of malware, including ransomware, is injecting malicious script or disguising the virus as a fake software crack download (mostly torrent). This method is known to be the primary distribution tactic for STOP/DJVU ransomware developers. The cybercriminals target people who are trying to install and activate paid software for free using peer-to-peer file sharing channels. Unfortunately, this can lead to a severe computer infection and data loss. What is also really bad is that people who look up such downloads are also highly likely to ignore security software warnings and proceed to open such downloads anyway.

Victim’s who have been infected with STOP/DJVU malware versions, including EFDC virus, report attempting to download illegal versions of these popular programs:

• Adobe Photoshop;
• Corel Draw;
• Cubase;
• Adobe Illustrator;
• Windows activation tools such as KMSPico.

We strongly recommend you to avoid posing risk to your computer’s security and your privacy and choose legitimate software download sources only. We can assure you that software licenses cost way less than hefty ransom amounts that cybercriminals try to extort from their victims.

Another popular way to spread computer threats including ransomware is malicious email spam. All that it takes for the cybercriminal to use this method is to compose a convincing email message, potentially spoof the sender’s address (to make sender’s address look legitimate, although it is not the original sender’s address), craft a malware-injected document and attach it to the email. Once the victim opens the attachment, the ransomware will launch on the system, or will be downloaded from an external source and executed then.

Internet criminals tend to name such attachments as invoices/payment information/parcel tracking information/missing or pending payment and similar. We suggest that you stay away from emails that seem at least slightly suspicious, get marked as spam, or simply if the arrival of such email makes you confused because you were not awaiting for such email at all. If you feel that the sender has no business with you (or at least shouldn’t have any in the current period of time), avoid interacting with such email’s contents, included links or attachments.

Victims of STOP/DJVU ransomware variants should stop searching for shady decryption tools on suspicious online websites. IMPORTANT. Other ransomware strain operators are uploading fake decryption tools online that deliver second ransomware payload on already compromised computers. One of such ransomware families that’s been noticed using this distribution technique is ZORAB.

Remove EFDC Ransomware Virus and Decrypt Your Files

Now that you have fallen victim to a ransomware attack, you must take actions to cleanse your computer from malware remains still lurking on the system and also do something to protect it from further attacks. That is why we recommend getting INTEGO Antivirus, a robust antivirus solution that provides real-time protection and a set of other highly useful security features. Additionally, you can download RESTORO to repair virus damage caused on Windows OS files.

After a complete EFDC ransomware virus removal, please read these recommendations:

• Report cybercrime incident to your local authority responsible for handling such events.
• Use data backups to restore your files, although remember that you must completely remove the malware first.
• Follow all the given instructions to decrypt or repair files affected by STOP/DJVU versions.
• We also recommend that you change your passwords, especially for websites that you save login credentials for in your browser.

OUR GEEKS RECOMMEND

Our team recommends a two-step rescue plan to remove ransomware and other remaining malware from your computer, plus repair caused virus damage to the system:

STEP 1. REMOVE AUTOMATICALLY WITH ROBUST ANTIVIRUS

REMOVE & PROTECT WITH INTEGO

Get INTEGO ANTIVIRUS for Windows to remove ransomware, Trojans, adware and other spyware and malware variants and protect your PC and network drives 24/7.. This VB100-certified security software uses state-of-art technology to provide protection against ransomware, Zero-Day attacks and advanced threats, Intego Web Shield blocks dangerous websites, phishing attacks, malicious downloads and installation of potentially unwanted programs.

Use INTEGO Antivirus to remove detected threats from your computer.

Read full review here.

STEP 2. REPAIR VIRUS DAMAGE TO YOUR COMPUTER

DOWNLOAD RESTORO

RESTORO provides a free scan that helps to identify hardware, security and stability issues and presents a comprehensive report which can help you to locate and fix detected issues manually. It is a great PC repair software to use after you remove malware with professional antivirus. The full version of software will fix detected issues and repair virus damage caused to your Windows OS files automatically.

RESTORO uses AVIRA scanning engine to detect existing spyware and malware. If any are found, the software will eliminate them.

Read full review here.

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Norbert Webb

Norbert Webb is the head of Geek’s Advice team. He is the chief editor of the website who controls the quality of content published. The man also loves reading cybersecurity news, testing new software and sharing his insights on them. Norbert says that following his passion for information technology was one of the best decisions he has ever made. “I don’t feel like working while I’m doing something I love.” However, the geek has other interests, such as snowboarding and traveling.