xDedic is among the largest and most damaging marketplaces on the dark web. Six months ago, business risk intelligence firm Flashpoint discovered it had a data set with information belonging to more than 85,000 organizations.

Cybercriminals use xDedic to buy access for compromised Remote Desktop Protocol (RDP) servers, which provide a convenient way to enter online systems, especially in companies with remote IT staff.  RDP is Microsoft's proprietary protocol, which lets users connect to other machines over the network and enables admins to remotely control servers and PCs.

Flashpoint has been watching xDedic for at least two years, says research director Vitali Kremez. The marketplace has been in operation since 2014 and has built a reputation among cybercriminals, who break into businesses' RDP servers so they can resell credentials online.

Hackers typically gain RDP access by first scanning the web for specific ports that link to Microsoft remote desktop protocols, Kremez explains. After identifying servers with the open port, they use brute force to test username and password combinations until a match is found.

Once they have access, they put the server up for sale and update administrator privileges. Anyone who buys credentials has a point of entry into the corporate network, which enables them to steal data, elevate privileges, launch external attacks, deploy ransomware, plant malware, manipulate network settings, and conduct account takeovers.

Their break-in tactics are most effective on short, weak server passwords and struggle against passwords that are longer and more complex, Kremez explains. However, large botnets can help attackers gain RDP access even when credentials are strong.

Kremez explains how threat actor "thedarkoverlord," known for breaching healthcare organizations, allegedly used this data set for at least some breaches. Healthcare is a frequently targeted sector, because access to open RDPs could give valuable data to cybercriminals.

"We had been investigating healthcare breaches," he continues. "One theme we noticed is, a lot of hospitals were breached because of exposed RDP servers."

However, it isn't the most frequently targeted industry.

The data set with information from more than 85,000 servers is representative of which industries are popular among hackers. Data analysis revealed the most exploited sectors are education, healthcare, legal, aviation, and government. The United States, Germany, and Ukraine are the more frequently targeted countries.

"Education is among the most unsecure; the most susceptible," says Kremez, noting how universities are easy to break into via brute-force attack. However, both universities and healthcare organizations have information-sharing communities through which they can share information about attacks and improve their infosec procedures.

Kremez believes the threats in xDedic will continue to grow in the future, especially after the recent Shadow Brokers release. If criminals continue to develop their toolkits and leverage exploits from the leak, they will cause even more damage if they can expand their access to other networks. While these exploits will have less of an impact because they aren't zero-days anymore, they can still prove dangerous, he says.

Businesses can protect themselves by not allowing their servers to be externally available and maintain proper access control, Kremez suggests. While it's convenient for technicians and network procedures to have servers available online, it's dangerous because cybercriminals typically try to brute-force access via externally available RDP servers.

He also advises taking password precautions. "Change passwords frequently, and make those passwords as complex as possible," he continues. "At the very least, it will thwart xDedic attackers."

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