Threat actors are using a previously discovered distributed denial-of-service (DDoS) attack tool dubbed XOR DDoS to launch upwards of 20 DoS attacks a day against targets in Asia and other parts of the world, new research showed.

A High-Bandwidth DDoS Attack

The attacks have ranged in bandwidth from less than 10 Gbps to over 150 Gbps and have been focused mainly on the gaming and education sectors, said content delivery network services provider Akamai in its “State of the Internet” report released this week. Akamai said it has mitigated several XOR DDoS attacks directed against its clients, including two in August, one of which generated nearly 179 Gbps of traffic, while the other measured nearly 109 Gbps in size.

Security researchers first detected XOR DDoS in September 2014. It is basically a DDoS attack tool that threat actors have been using to hijack Linux machines and build large botnets for launching denial-of-service attacks. Akamai described XOR DDoS as an example of a small but growing number of Linux-based malware tools being used in DDoS attacks. Other examples include the Spike DDoS toolset and IptabLes and IptabLex toolkits.

Shift to Linux

Typically, threat actors have gone after Windows-based machines when building botnets for launching DoS attacks. But the growing number of Linux vulnerabilities being discovered these days has given threat actors another target to go after, Akamai noted.

XOR DDoS itself does not target any specific Linux vulnerability. Instead, it spreads through improperly protected Secure Shell (SSH) services. Cybercriminals obtain login credentials to the SSH service on Linux machines using brute-force attacks. They then use root-level privileges to download and execute malware, Akamai said.

The IP addresses of the command-and-control servers used to control the botnet and the source IP addresses of the bot network suggest that the malware is of Asian origin, Akamai noted. The company added that the XOR DDoS botnet has grown considerably in size since researchers first detected it last year.

Diversionary Extortion Tool

The XOR DDoS attack tool is an example of what some security researchers say is a growing interest in the use of DDoS attacks as a diversionary tactic or an extortion tool among threat actors.

For instance, DD4BC, a cybercrime group that has been active since last September, has been using the threat of DDoS attacks to try to extort money from businesses around the world. An Akamai alert about the group from earlier in the year said DD4BC has hit at least 114 of its customers with DDoS attacks since April. The attacks averaged around 13.34 Gbps, with some having peak bandwidth in excess of 23 Gbps.

Growing Threats

In a Verisign report released earlier this year, the domain name specialist noted a sharp increase in the availability of DDoS-for-hire services making it possible for almost anyone to launch DoS attacks against targets of their choice. According to Verisign, in some cases it’s possible to get skilled cybercriminals to launch a DDoS attack against a specified target for as little as $2 per hour.

“The increasing availability of DDoS-for-hire services … presents a huge risk for security professionals,” the Q4 2014 version of the report warned.

At the same time, the average DDoS attack size has also been steadily increasing. Some 34 percent of attacks that Verisign reviewed peaked at between 1 and 5 Gbps, while 10 percent or so of the attacks had a peak bandwidth of over 10 Gbps. The IT services industry, including cloud providers and software-as-a-service (SaaS) organizations, are the most frequent targets of DDoS attacks. Also heavily targeted are organizations in the financial services industry and, increasingly, public-sector organizations, Verisign said in its report.

These new trends present a new challenge for security professionals. Remaining aware of growing trends and assessing for vulnerabilities that could be exploited is critical.