An automated attack targeting users of the open source Rejetto webserver and file-sharing application tried to inject the IptabLes DDoS tool.

Apparently no vulnerability is too small, no application too obscure, to escape a hacker’s notice.

A honeypot run by Trustwave’s SpiderLabs research team recently snared an automated attack targeting users of the open source Rejetto HTTP File Server (Rejetto HFS). Someone was trying to exploit a vulnerability—which has since been patched—and install the well-known distributed denial-of-service tool IptabLes (unrelated to the Linux tool), also known as IptabLex.

Rejetto HFS has been downloaded more than 24,000 times in the last seven days and according to the project’s website has an estimated 12,500 users and is used as a file-sharing application as well as a webserver. It also runs on Wine, the Windows emulator for Linux systems.

“This is just one snapshot, one request. This is one example to extrapolate and take a higher level view; there’s likely a lot more activity out there,” said Ryan Barnett, SpiderLabs lead researcher.

It’s likely the attackers have simply incorporated this exploit into a larger attack platform, Barnett said.

“That’s the value of honeypots, spotting automated tools scanning the Internet shot-gunning exploits, and hoping it works,” Barnett said.

The exploit, sent from a possible compromised IP address in China, was targeting CVE-2014-6287, a remote code execution bug in Rejetto. Specifically, the vulnerability affects Rejetto versions prior to 2.3c; the vulnerability is in the findMacroMarker function. Barnett said the exploit relies on a null byte character to trigger the attack code, which is written in Microsoft VBScript.

Once the exploit executes, it tries to connect to a pair of IP addresses hosted in Paris (123[.]108.109.100 and 178[.]33.196.164) on three ports: 80 (HTTP); 53 (DNS); and 443 (HTTPS). Barnett said only 178[.]33.196.164 remains online and is a malware repository responding to XML HTTP Requests (XHR) from the exploit.

The exploit tries to infect Rejetto users with the IptabLes DDoS tool. via @Threatpost Tweet

A file called getsetup.exe is sent to the compromised server along with another executable, ko.exe, which drops IptabLes. Barnett said detection rates are high for the hash of getsetup.exe. IptabLes is a troublesome DDoS tool, capable of synflood and DNSflood attacks. It installs itself into boot for persistence, according to the SpiderLabs research, which added that IptabLes has been widely reported targeting Linux and Unix servers.

The vulnerability being targeted was submitted last September.

“It’s not very sophisticated, and a lot of times these types of attacks don’t have to be,” Barnett said. “These guys are concerned with scale because they’re running botnets. What makes botnets so nice to the criminals running them is that they don’t care to be stealthy. They can send attacks blindly, and if they’re shut down, they just move on.”