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njRAT Infections on the Rise: Security Firms

The notorious remote access Trojan (RAT) known as njRAT is making a comeback, according to security firms Zscaler and PhishMe.

In June 2014, Microsoft attempted to disrupt the njRAT (Bladabindi) and NJw0rm (Jenxcus) malware families. Now, after several months in which there haven’t been any major developments, researchers say they have noticed an increase in njRAT infections.

The RAT, developed in .NET, allows attackers to take complete control of an infected device. The malware is capable of logging keystrokes, downloading and executing files, providing remote desktop access, stealing application credentials, and accessing the infected computer’s webcam and microphone.

PhishMe reports that njRAT has been distributed over the past period with the aid of spam emails advertising a car changer hack for the “Need for Speed: World” video game. Zscaler also noted that video game cracks and application key generators are often used as lure.

When Microsoft targeted njRAT in 2014, the company seized nearly two dozen domains belonging to dynamic DNS provider No-IP. Microsoft argued at the time that No-IP domains had been used 93 percent of the time for njRAT and NJw0rm infections. However, the DNS company lashed out at Microsoft for the way it handled the operation because the decision to seize the domains without any warning affected numerous legitimate customers.

Now, Zscaler and PhishMe report that No-IP services are still being abused by njRAT operators. Zscaler has identified more than 20 dynamic DNS services abused by malware authors for command and control (C&C) communications.

Zscaler has also noticed an increase in H-Worm infections. H-Worm, a VBScript-based RAT that shares code with njRAT, was analyzed by FireEye in September 2013 when it had been used in targeted attacks aimed at the international energy industry.

According to researchers, new H-Worm variants continue to emerge. Zscaler has tracked a total of 16 active variants in 2015.

“Despite Microsoft's attempts to disrupt the C&C channel for this notorious RAT back in June 2014, we continue to see the usage of various dynamic DNS services by the malware authors for it's C&C server communication. It remains one of the most popular and prevalent RATs in the wild today,” researchers wrote in a blog post.

In January, Trend Micro reported that the source code of NJw0rm, published on hacker forums in May 2013, had been used by malware developers to create new RATs. One of these new threats, dubbed “Sir DoOom,” emerged in December 2014. The malware can be used to carry out a wide range of tasks, including mine Bitcoin, launch DDoS attacks, take control of computers, and terminate antivirus processes.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.