Hackers controlling a “botnet” of over 20,000 infected WordPress sites are attacking other WordPress sites, according to a report from The Defiant Threat Intelligence team. The botnets attempted to generate up to five million malicious WordPress logins within the past thirty days.
Per the report, the hackers behind this attack are using four command and control servers to send requests to over 14,000 proxy servers from a Russian provider. Those proxies are then used to anonymize traffic and send instructions and a script to the infected WordPress “slave” sites concerning which of the other WordPress sites to eventually target. The servers behind the attack are still online, and primarily target the XML-RPC interface of WordPress to try out a combination of usernames and passwords for admin logins.
“The wordlists associated with this campaign contain small sets of very common passwords. However, the script includes functionality to dynamically generate appropriate passwords based on common patterns … While this tactic is unlikely to succeed on any one given site, it can be very effective when used at scale across a large number of targets,” explains The Defiant Threat Intelligence team.
Attacks on the XML-RPC interface aren’t new and date back to 2015. If you’re concerned that your WordPress account might be impacted by this attack, The Defiant Threat Intelligence team reports that it is best to enable restrictions and lockouts for failed logins. You also can consider using WordPress plugins which protect against brute force attacks, such as the Wordfence plugin.
The Defiant Threat Intelligence team has shared information on the attacks with law enforcement authorities. Unfortunately, ZDNet reports that the four command and control servers can’t be taken offline because they are hosted on a provider that doesn’t honor takedown requests. Still, researchers will be contacting hosting providers identified with the infected slave sites to try and limit the scope of the attack.
Some data has been omitted from the original report on this attack because it can be exploited by others. The use of the proxies also makes it hard to find the location of the attacks, but the attacker made mistakes which allowed researchers to access the interface of the command and control servers behind the attack. All of this information is being deemed as “a great deal of valuable data” for investigators.