This entry was posted in WordPress Security on December 18, 2017 by Mark Maunder 50 Replies

A massive distributed brute force attack campaign targeting WordPress sites started this morning at 3am Universal Time, 7pm Pacific Time. The attack is broad in that it uses a large number of attacking IPs, and is also deep in that each IP is generating a huge number of attacks. This is the most aggressive campaign we have seen to date, peaking at over 14 million attacks per hour.

The attack campaign was so severe that we had to scale up our logging infrastructure to cope with the volume when it kicked off, which makes it clear that this is the highest volume attack that we have seen in Wordfence history, since 2012.

The campaign continues to ramp up in volume during the past hour as we publish this post. A graph of the attack volumes is shown below which shows the number of attacks per hour and the number of attacking IPs that we see each hour.

Our infrastructure automatically blacklisted the participating IPs in real-time and distributed those to our Premium customers. This all happened unattended early this morning. We continue to monitor the campaign and are analyzing its origin and who is behind it.

What we know at this time:

The attack has so far peaked at 14.1 million attacks per hour.

The total number of IPs involved at this time is over 10,000.

We are seeing up to 190,000 WordPress sites targeted per hour.

This is the most aggressive campaign we have ever seen by hourly attack volume.

A possible explanation for this new massive increase in brute force attacks

On December 5th, a massive database of hacked credentials emerged. It contains over 1.4 billion username/password pairs. Approximately 14% of the database contains credentials that have not been seen before. The database is also searchable and easy to use.

Historically, brute force attacks targeting WordPress have not been very successful. This new database provides fresh credentials that, when matched with a WordPress username, may provide a higher success rate for attackers targeting sites that do not have any protection.

Protecting Yourself

If you have not already done so, install Wordfence immediately on your site. Even the free version of Wordfence provides excellent brute force protection by limiting login attempts and hiding usernames while employing a variety of other mechanisms to ward off attackers.

The Premium version of Wordfence uses a real-time IP blacklist to completely block attackers. Our real-time blacklist was automatically updated as this attack started early this morning to immediately block IPs engaging in the attack. As you can see from the chart above, we are already monitoring over 10,000 unique IPs and actively blocking them.

We strongly recommend that you upgrade to Wordfence Premium to benefit from the real-time blacklist feature which blocks any traffic from these malicious IPs.

Spread the Word

This is the highest volume brute force attack we have seen to date. It may also be using the fresh credentials that were provided in the database released on December 5th, so it may achieve a higher than normal success rate. Please spread the word among the WordPress community to create awareness of this new threat. You can suggest the following actions to your fellow WordPress site owners: