Thousands of Linux and FreeBSD Servers Infected by Spam-blasting Malware

The researchers reported on Wednesday that thousands of computers running the Linux and FreeBSD operating systems have been infected over the past seven months with a sophisticated malware. The malware make part of a perfidious network blasting the internet with spam. The malware likely infected many more machines during the five years it's known to have existed.

The malware known as Mumblehard has been designed by experienced and highly skilled programmers. It includes a backdoor and a spam daemon, which is a behind-the-scenes process that sends large batches of junk mail. These two main components are written in Perl and they are obscured inside a custom "packer" which is written in assembly, a low-level programming language that closely corresponds to the native machine code of the computer hardware it runs on.

The researchers have revealed evidence that Mumblehard may have links to Yellsoft, a company that sells DirecMailer, which is Perl-based software for sending bulk e-mail. The block of IP addresses for both Yellsoft and some of the Mumblehard C&C servers share the same range. The pirated copies of DirecMailer silently install the Mumblehard backdoor. The pirated copies are also obscure by the same packer used by Mumblehard's malicious components.

The Eset researchers suspect that the malware may take hold by exploiting vulnerabilities in the Joomla and WordPress content management systems. They also think that the infections are the result of installing pirated versions of the DirecMailer program.

 Eset observed around 9,000 IP addresses which cannot be directly correlated to the number of machines that were infected by Mumblehard, since in some cases more than one server may share an address and in other cases a single server may give up an old address and take up a new one. 

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by Malik korrich ~ jeudi 30 avril 2015 0 commentaires

Google’s VirusTotal puts Linux malware under the spotlight

The rise of malware designed to infect Linux servers has earned it greater attention from VirusTotal, the Google-owned go-to tool for malware hunters.

For security researchers that need to stay on top of emerging malware threats the VirusTotal malware database has become an integral tool. Anyone can upload a suspicious file to the web tool to check whether the dozen or so antivirus engines, such as Kaspersky,McAfee, Symantec, and others, detect it as malware. 

 The tool is meant to be used by the good guys, but as one researcher found last year, black hat hackers were also using the service to test their malware against antivirus products prior to releasing it in the wild — despite the tool's shortcomings for comparative analysis.

While Virus Total maintains detailed information about malicious files affecting Windows, Linux malware has remained something of a blind spot for the tool, in part because such malware is much rarer.
The tool offered basic information about each Linux file sample, but lacked additional information that AV companies and researchers were given for Windows malware.

That situation might have been fine in the past. However, over the past two years, a new breed of Linux malware has emerged whose chief targets are not PCs but vulnerable web servers.

In part due to the lack of information, antivirus vendors were slow to respond to Linux malware samples, often submitted as ELF files — the standard binary file format for executables, object code, shared libraries, and core dumps for Unix and Unix-like systems. As such, detection rates by AV vendors remained low. Now the number of ELF files submitted is rising: in the last week alone, there were over 35,000 suspicious ELF files submitted to VirusTotal, slightly less than the 44,000 suspicious Microsoft Word files uploaded.

VirusTotal announced on Tuesday that it will be addressing the shortcomings with the web tool for Linux malware. "Even though the popularity of the Windows OS among average end-user systems has meant that attackers have mostly focused on developing malware for Windows systems, ELF badness is a growing concern," the Google subsidiary wrote in a post on Tuesday.

Read more about this Linux malware on ZDNET

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by Malik korrich ~ mercredi 12 novembre 2014 0 commentaires