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In the past few weeks, many WordPress blogs have been under a large-scale brute force attack. These attacks use brute-force techniques to log into WordPress dashboards and plant malicious code onto compromised blogs and websites.

It’s important to note what these attacks aren’t. They are not compromising WordPress blogs using known vulnerabilities in unpatched versions; if anything this current attack is less sophisticated than that – it merely tries to log into the default admin account with various passwords. If it is successful in logging in, it adds code for Blackhole Exploit Kit redirection pages to the blog.

We have been monitoring these attacks, and we can confirm that they are indeed taking place. Because they add distinctive URLs to the blogs they have compromised, we can identify the scale of this attack, as seen by the Smart Protection Network.

Over a one-day period, we identified more than 1,800 distinct sites that had been compromised by this attack. This represents a significant increase over the typical number of compromised WordPress sites that we encounter over the same period, highlighting the increased activity related to this particular campaign.

Both users and site administrators can help mitigate threats like these. This particular attack only targeted administrator accounts that had not changed their default login name (admin). It is advisable that users change this to another login name of their choice. These and other steps to mitigate against this attack are outlined in WordPress’s online manual.

As for users, because compromised sites like these are used by exploit kits, a good way to reduce these threats is to keep the software installed on your system up to date. Many applications today include some form of automatic updating, which (unfortunately) many users ignore. We have covered some of this in our guides on using Java and Flash safely in the past, which can be checked for reference.

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