Botnet Guesses Weak Passwords to Compromise Thousands of Web Servers

Researchers study a botnet campaign that has stolen control of approximately 6,000 servers just by guessing 10 to 100 passwords per site.

With all the focus on convincing users to strengthen their passwords, brute-force guessing attacks should no longer be effective. Yet, recently, a discovered botnet has been able to build a stable of approximately 6,000 servers just by guessing 10 to 100 passwords per site, researchers from Arbor Networks said Aug. 7.

The Fort Disco campaign uses a botnet of nearly 25,000 Windows machines to attempt to compromise more bandwidth-capable content-management servers running WordPress and Joomla, the researchers stated in the analysis. Most of the compromised Websites are located in Russia and the Ukraine, and the success of the campaign shows that many administrators still do not consider security when choosing their passwords, Matt Bing, senior research engineer for Arbor Networks, told eWEEK.

"If you actually look at the passwords that successfully logged on to these sites, they are the weakest of the weak—ones like 'admin' and '123456,'" he said.

While the Fort Disco campaign shows similarities to previous compromises of Web servers, the only clues to the motivation of the attackers is the installation of a PHP backdoor and tools for creating a drive-by download site on about 800 of the compromised servers.

The campaign shows similarities to the Brobot attacks that enabled the al Qassam Cyber Fighters to inundate financial services firms with multi-gigabit-per-second attacks, slowing consumers' access to bank accounts. The servers used in that attack appeared to be content-management servers that had been compromised though password guessing.

"We were not able to find any connection to the Brobot attacks," Bing said. "That was the first thought I had."

Gaining access to servers and gathering information on the victims is the only way to get a good picture of a particular botnet campaign, Bing wrote in the analysis. Typical malware analysis will only allow an analyst to know the capabilities of an attacker. But gaining access to the command-and-control servers will allow additional information on the victims and the targets of the attacks.

"Understanding an attack campaign by only analyzing a malware executable file is a Sisyphean task," he wrote. "The malware alone can be picked apart by disassemblers, poked and prodded in a sandbox, but by itself offers no clues into the size, scope, motivation and impact of the attack campaign."

The top countries hosting the Windows botnet used by attackers to spread the infection are the Philippines, Peru and Mexico, Arbor stated. The top-five passwords that succeeded in compromising Web servers include "admin," "123456," "123123," "12345" and the Web server's domain name.

While attributing attacks to a specific group is difficult, the researchers noted that many of the victims' Web servers were in Russia, as were the command-and-control servers. In addition, many comments and file names were in Cyrillic, the Russian alphabet.

Robert Lemos

Robert Lemos

Robert Lemos is an award-winning freelance journalist who has covered information security, cybercrime and technology's impact on society for almost two decades. A former research engineer, he's...