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Well Known Trojan "Rakhni" Can Now Mine!

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By: Manu

August 10, 2018

Well, Rakhni is not a new Trojan if you follow cyber security news, but what's new is that Rakhni has a new cryptomining module added to it!

Cryptomining started taking over the ransomware trend with the new developments in cyptocurrencies.

With the added module, Rakhni can now analyze the infected machine and choose between encrypting or mining. Well, that is bad news, but how it works is interesting.

This behavior was first detected in India, Russia, Ukrain, Germany, and Kazakhstan. The distribution method was identified as spam emails, which contain a malicious docx financial document file. This is disguised as a financial document and seems to be received by employees in large scale companies.

When the user opens and allows editing, the program requests to install an executable file, which seems to be installing a file viewer.

Rakhni starts its work!!!

It shows an error message why nothing happens and then starts, and then the horse is already inside the city (The city being your machine, of course)!Rakhni first disables the Windows Defender and installs forged certificates.Then it waits until the time comes while analyzing the infected computer to decide whether to run a minor or demand a ransom.Finally, it searches for connections and networks that the infected computer is connected to and propagates or copies itself.

How Rakhni Decided Whether to Run an Encryptor and Demand Ransom or Use the Machine as a Minor

This is where it gets interesting.While the user doesn't know anything about the Trojan, Rakhni analyzes the computer to retrieve several detections.

It looks for any files in the machine that says "cryptocurrency," "bitcoins," or any keyword related to the now very popular and expensive cryptocurrencies. Found any positive detections? BAM!! It decides to encrypt and demand a ransom in Bitcoin, of course, which cannot be tracked if it's not exchanged for real currency.

No such detections?  Rakhni runs a signature check of the machine and retrieves data on the memory, power, and the strength of the machine overall. If it has good resources and is a suitable candidate to be used as a minor, well you guessed it. Your machine will become a mining slave.

Rakhni tries its best to keep its existence in a low profile and propagates to other machines connected!

This piece of malware is impressively complex and beautifully executed. But it's used for a bad cause at the end. The minds behind these masterpieces should be used to do some good in the world. That's what I believe in.

How to Avoid Being a Victim

Kaspersky already has a Rakhni decryptor, as it's a ransomware that came into existence around 2013. But as the mining behavior is new, there's no proper remediation for it yet, rather than to prevent it before it happens.

How to Prevent the Rakhni Trojan

As this malware  focuses on corporate personnel and attacks via social engineering-based spam mails, prevention methods include the following:

  • The companies can conduct employee awareness workshops to educate employees on these forms of malware.
  • Create use cases to send these types of spam directly to the deleted folder of the corporate email service provider.
  • Always having a backup of sensitive information.
  • Provide a thorough training for the information security team on threat detection and mitigation.
  • Do regular system checks and search for anomalies in used machine resources and background processes.
  • Initiate spam simulations within the company and do research on how many employees fall for the trap and how many report the threat.
  • Block or nullify any links that come in mail before it reaches the user (This can be done through the security probes and may available in the mail client. E.g., MS Outlook provides this service by default).
  • Use behavioral detection-based host and network Virus Guards and IPS

It's always important to be safe from cyber intruders in the 21st century; almost all the information is digitalized and stored online. IoT concepts make it harder for security implementation, and it's impossible to create a 100% safe environment for information. But it's always better to be prepared!

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