Malicious Java app infects Mac, Linux systems with DDoS bot

Criminals are once again using Java’s cross-platform design to add Linux and Mac users to their usual Windows target list, Kaspersky Labs researchers have discovered.

The malicious Java application recently unearthed by the firm, HEUR:Backdoor.Java.Agent.a, is only the latest example of the opportunistic trend to use the huge potential of Java to get a malware three-for-one in the cause of turning systems into Distribued Denial of Service bots.

Once on the target system after hitting Java flaw CVE-2013-2465 (SE 7 Update 21 and earlier), patched last June, the malware sets up its command and control using IRC. According to Kaspersky, one of the targets on the receiving end of a DDoS attack might be an unnamed bulk email service.

It also deploys the Zelix Klassmaster obfuscator as a technique meant to frustrate analysis.

“In addition to obfuscating bytecode, Zelix encrypts string constants. Zelix generates a different key for each class—which means that in order to decrypt all the strings in the application, you have to analyze all the classes in order to find the decryption keys,” said Kaspersky Lab researcher, Anton Ivanov.

Familiar tactics

The cross-platform tactic isn’t new and in truth it’s hard to know whether the criminals behind it are more interested in attacking Linux and Macsa> or simply targeting Java’s numerous vulnerabilities on the greatest number of systems. In December, DDoS malware targetting both Windows and Linux was reported by Poland’s national CERT, albeit without the Java angle.

“Over the past year we have seen many samples of malware with different capabilities, some with DDoS abilities and automation through an IRC command and control,” said Barry Shteiman, director of security strategy at security firm Imperva.

“The choice of Java in this case does make the malware piece more modern. Java is multiplatform and therefore will allow the malware to run on more platforms. It may also use the fact that hackers are very focused on Java now for vulnerability research, so there is a likelihood that the malware can evolve with new ways to exploit and onboard a system,” he said.

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