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Docm file virus: what is it and how to remove

3 min read
It’s a good security measure to keep macros in Docm files disabled these days, because ransomwares like Locky and Zepto use them to compromise computers.

There’s a sensible reason why the devs at Microsoft chose to keep macros in Office documents turned off by default. The exploitation of these VBA-based scripts is one of the popular and rising PC contamination vectors. This technique was heavily used by the distributors of Dridex, a banking Trojan that stole multiple sensitive financial records. The makers of ransomware, a type of malicious code that encrypts one’s data in pursuit of a buyout from the victims, recently began harnessing macros-related vulnerabilities to deploy their offending executables on systems. To this end, they are sending out thousands of spam emails in one hit, where the attachments are files with .docm extension. When opened, these documents are configured to produce a security warning asking the user to enable macros.

Example of phishing email with Docm file on board
Example of phishing email with Docm file on board

The peddlers of the ransom Trojan called Locky leveraged this methodology in the following way: the Docm file originally contained some text that looked like gobbledygook. A prompt in it said that by turning macros on the user would rectify the data encoding and thus be able to understand the content. Another sample of malicious crypto code dubbed Zepto, in its turn, does basically the same thing but displays a blank document instead, with the macros activation request popping up at the top. A big problem with these malware spreading tactics is that a lot of the phishing emails are targeted, therefore the recipients don’t anticipate any issues and open them with confidence that some important documents are inside for real.

Docm document with rogue security warning
Docm document with rogue security warning

The ostensible authenticity of these spear phishing messages has got numerous users infected over the last few months. In a recent surge of breaches, the attached Docm files have been delivering the Zepto ransomware to machines. The threat actors exploit security weaknesses in Visual Basic for Applications, which is what macros are built with, to compromise computers in a stealthy fashion. The ransomware loader drops the malicious executable to the Temp path. When launched for the first time, the random named process scans all fixed drives, removable ones and network shares (both mapped and unmapped) in order to locate all the potentially valuable files.

Zepto ransom instructions
Zepto ransom instructions

Then, the malign program applies two cryptographic algorithms, RSA-2048 and AES-128, to encrypt the detected personal data. As a result of this, every such file will be renamed to a long string of unrelated characters followed by the .zepto extension. Since the private RSA key, which is necessary for decryption, is nowhere to be found on the infected PC, the criminals can dictate their own terms. Using the documents named _HELP_instructions.html and _HELP_instructions.bmp, the extortionists explain to the victim that he or she needs to follow a special Tor link and pay 0.5 BTC (321 USD at the time of writing) on the personal decryptor page.

To avoid the Zepto virus, think twice before opening email attachments that seem odd. Also, do not enable macros in Docm files unless it’s absolutely necessary. Find some further troubleshooting advice in the next section of this post.

Docm ransomware automated removal and data recovery

Owing to an up-to-date database of malware signatures and intelligent behavioral detection, the recommended software can quickly locate the infection, eradicate it and remediate all harmful changes. So go ahead and do the following:

1. Download and install the antimalware tool. Open the solution and have it check your PC for PUPs and other types of malicious software by clicking the Start Computer Scan button

Download Docm virus remover

2. Rest assured the scan report will list all items that may harm your operating system. Select the detected entries and click Fix Threats to get the troubleshooting completed.

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

Ransomware Prevention Tips

To avoid Docm 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 Docm ransomware removal tool

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