Security Experts:

Cybercriminals Abuse Amazon Cloud to Host Linux DDoS Trojans

Cloud services provided by Amazon and other companies are being abused by profit-driven cybercriminals to host DDoS bots, Kaspersky Lab reported on Friday.

Earlier this month, researchers published an analysis of a sophisticated Linux Trojan (Backdoor.Linux.Mayday.f) capable of conducting DNS amplification DDoS attacks. After further investigation, Kaspersky identified two new variants of this threat, which the security firm detects as Backdoor.Linux.Mayday.g.

One of the new variants has DNS amplification functionality that's similar to Backdoor.Linux.Mayday.f. The other new variant has been seen on compromised Amazon EC2 server instances and is designed to flood websites with UDP traffic only, Kaspersky said.

"The flow is strong enough that the DDoS'd victims were forced to move from their normal hosting operations IP addresses to those of an anti-DDoS solution. The flow is also strong enough that Amazon is now notifying their customers, probably because of potential for unexpected accumulation of excessive resource charges for their customers," Kaspersky Lab researcher Kurt Baumgartner wrote in a blog post.

According to Kaspersky, the attackers are hacking into EC2 instances by exploiting a vulnerability in versions 1.1.x of Elasticsearch, an open source search and analytics engine that's often used in cloud environments, including Microsoft Azure and Amazon EC2. The Elasticsearch flaw leveraged by the attackers (CVE-2014-3120) has been patched with the release of versions 1.2 and 1.3, but the vulnerable version is still used in active commercial deployments by some organizations.

The Elasticsearch exploit is used to deliver Backdoor.Perl.RShell.c, a Perl Web shell that allows the attackers to fetch the DDoS bots.

In cases where they need higher privileges to accomplish their goals, the attackers rely on exploits that enable them to escalate privileges on Linux. Experts have spotted source code for two exploits, CVE-2014-0196 and CVE-2012-0056, which attackers most likely compile on compromised hosts only when needed.

While the threats analyzed by Kaspersky have been seen on Amazon EC2 instances, Baumgartner points out that this isn't the only platform abused by cybercriminals.

The security firm observed attacks powered by these DDoS bots against a large regional bank in the United States, and a large electronics maker and service provider located in Japan.

In addition to powering DDoS attacks, Solutionary reported in June that the number of malicious elements hosted by Amazon Web Services almost tripled compared to the end of 2013.

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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.