Cloud services end up abused by profit-driven cybercriminals to host distributed denial of services (DDoS) bots, researchers said.

Earlier this month, researchers from Kaspersky Lab 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.

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One of the new variants has DNS amplification functionality that’s similar to Backdoor.Linux.Mayday.f. The other new variant was on compromised Amazon EC2 server instances and can flood websites with UDP traffic only, Kaspersky researchers 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.

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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 often used in cloud environments, including Microsoft Azure and Amazon EC2.

The Elasticsearch flaw leveraged by the attackers (CVE-2014-3120) ended up patched with the release of versions 1.2 and 1.3, but the vulnerable version still sees use in active commercial deployments by some organizations.

The Elasticsearch exploit can 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.

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