There’s a new malware family in town – and one that attacks Linux systems by concealing itself in legitimate binaries to deliver several backdoor and rootkits.

Dubbed FontOnLake, by cybersecurity researchers at ESET, samples of the malware date as far back as May 2020. According to researchers, the malware makes use of several carefully crafted modules that not just collect credentials, but also give remote access to the threat actors. Vladislav Hrčka, malware analyst and reverse engineer at ESET, commented:

“The sneaky nature of FontOnLake’s tools in combination with advanced design and low prevalence suggest that they are used in targeted attacks.”

Trojanized utilities

Hrčka notes that all the malware disguises itself inside trojanized versions of standard Linux utilities, including cat, kill, and sshd. In fact, one of the samples the researchers analyzed was created specifically for CentOS and Debian. However, the exact mechanism employed by the threat actors to replace the original utilities with the malicious ones remains a mystery.

Analyzing the malware, the researchers note that the samples contained three custom backdoors written in C++, which gave remote access to the infected machines to the operators of the malware.

The location of the Command and Control (C2) server and the countries from which the samples were uploaded indicate that the attackers were after targets based in Southeast Asia. Hrčka also added:

“Following our discovery while finalizing our white paper on this topic, vendors such as Tencent Security Response Center, Avast and Lacework Labs published their research on what appears to be the same malware.”

Hrčka concluded that ESET’s products can flag all the components of the malware.

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