Erebus Ransomware Targets Linux Servers

Linux – not so secure after all.

The IT security researchers at Trend Micro recently discovered malware that has the potential to infect Linux-based servers. The malware, called Erebus, has been responsible for hijacking 153 Linux-based networks of a South Korean web-hosting company called NAYANA.

NAYANA’s clients affected

Erebus is a ransomware capable of infecting Linux operating systems. As such, around 3,400 of NAYANA’s clients were affected due to the attack with databases, websites and other files being encrypted.

The incident took place on 10th June. As of now, NAYANA has not received the keys to decrypt their files despite having paid three parts of the ransom. The fourth one, which is allegedly the last installment, is yet to be paid. However, according to NAYANA, the attackers claimed to provide the key after three payments.

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What is Erebus?

According to Trend Micro’s report, Erebus was originally found back in September 2016. At the time, the malware was not that harmful and was being distributed through malware-containing advertisements. Once the user clicked on those ads, the ransomware would activate in the usual way.

The initial version of the Erebus only affected 423 file types and did so using the RSA-2048 encryption algorithm, thereby encrypting the files with the .encrypt extension. Furthermore, it was this variant that was using a number of websites in South Korea as a command-&-control (C&C) center.

Later, in February 2017, the malware had seemingly evolved as now it had the ability to bypass User Account Control (UAC). For those who may be unfamiliar with UAC, it is primarily a Windows privacy protection system that restricts anyone who is not authorized, to alter the user’s computer.

However, this later version of the Erebus was able to do so and inject ransomware ever so conveniently. The campaign in which this version was involved demanded a ransom of 0.085 bitcoins – equivalent to USD 216 at present – and threatened to delete the files in 96 hours if the ransom was not paid.

Now, however, Erebus has reached new heights by having the ability to bypass not only UAC but also affect entire networks that run on Linux. Given that most organizations today use Linux for their networks, it is no surprise to see that the effects of the malware are far-reaching.

How does the latest Erebus work?

According to Trend Micro, the most recent version of Erebus uses RSA algorithm to alter the AES keys in Windows and change the encryption key as such. Also, the attack is accompanied by a Bluetooth service so as to ensure that the ransomware does not break, even after the computer is rebooted.

This version can affect a total of 433 file types including databases, archives, office documents, email files, web-based files and multimedia files. The ransom demanded in this campaign amounts to 5 bitcoins, which is USD 12,344 currently.

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Erebus is not the first of its kind

Although ransomware affecting Linux based networks are rare, they are, however, not new. Erebus is not the first ransomware to have affected networks running on Linux. In fact, Trend Micro claims that such ransomware was discovered as far back as in 2014.

Some of the ransomware include Linux.Encoder, Encrypter RaaS, KillDisk, KimcilWare and much more. All of these were allegedly developed from an open-source code project that was available as part of an educational campaign.

The ransomware for Linux, despite being somewhat inferior to those for Windows, are still potent enough to cause damage on a massive scale. This is because, a number of organizations and data centers use Linux, and hijacking such high-end systems can only mean catastrophe.

Safety precautions

To avoid any accidents happening, IT officials and organizations running Linux-based networks need to take some serious precautions. The most obvious one is to simply keep the server updated with the latest firmware and anti-virus software.

Furthermore, it is always a good idea to keep a back-up of your data files in two to three separate locations. It is also repeatedly advised to avoid installing unknown third-party programs as these can act as potential gateways for such ransomware.

Lastly, IT administrators should keep monitoring the traffic that passes through the network and looks for anomalies by identifying any inconsistencies in event logs.

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