Arbor Networks, more than 6,000 sites have been compromised in a spate of brute force attacks launched by a botnet dubbed Fort Disco. Made up of more than 25,000 PCs, the botnet receives a list of sites to attack from a central command and control server. On some of the sites, a variant of the "FilesMan" PHP backdoor is installed by the attackers.
"By uploading a PHP shell to compromised sites, an attacker can easily issue commands to thousands of compromised sites in seconds," Matt Bing, a research analyst at Arbor Networks' ASERT team, notes in a blog post. "Blogs and CMSs tend to be hosted in data centers with immense network bandwidth. Compromising multiple sites gives the attacker access to their combined bandwidth, much more powerful than a similarly sized botnet of home computers with limited network access by comparison."
In a handful of cases, researchers found drive-by exploit kit tools, but we have no evidence the attacker actually used them to target visitors to the compromised sites, Bing tells Dark Reading. In particular, some of the sites contained a PHP-based redirector that sent Windows users running Internet Explorer, Firefox, or Opera to a series of sites before ultimately landing on one with the Styx exploit kit.
There are at least four variants of the malware used in the attack. Once on an infected system, the malware receives commands from the attacker that include a URL of a list of sites to attack. According to Arbor Networks, the target list can be anywhere from 5,000 to 10,000 sites at a time. Included in the commands is the password to use or a URL to a password list. The malware also has a URL of usernames hardcoded, and will attempt to login to the sites with combinations of the usernames and passwords.
The most common password was "admin," which worked 893 times. The next most popular was "123456," which worked on 588 of the compromised sites.
"The number of weak passwords is not surprising, as this campaign is clearly a target of opportunity and not focused on a specific target," Bing says. "This is interesting as it marks a sea change in the tactics of attackers. In addition to drive-by exploits of unpatched Windows machines being the low-hanging fruit, attackers are learning that these blog and content management systems are often vulnerable to trivial attacks."
The attackers behind the campaign are believed by Arbor Networks to be from a post-Soviet state due to the fact that the majority of the sites being targeted are in Russia or the Ukraine, as are all of the command and control sites. In addition, a Russian error string was found on several command and control sites.
The top three countries in terms of infections are the Philippines, Peru, and Mexico.
"Beginning with the Brobot attacks in early 2013, we’ve seen attackers focusing on targeting blogs and content management systems," Bing blogs. "This marks a tactical change in exploiting weak passwords and out-of-date software on popular platforms."
"While we have no evidence the Fort Disco campaign is related to Brobot or denial-of-service activity, we’ve experienced the threat that a large blog botnet can deliver," he writes.
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Brian Prince is a freelance writer for a number of IT security-focused publications. Prior to becoming a freelance reporter, he worked at eWEEK for five years covering not only security, but also a variety of other subjects in the tech industry. Before that, he worked as a ... View Full Bio