For the second time, a hacker (in the swine sense of the word) broke in and defaced Oddhead Blog. Once again, I’m left impressed by the ingenuity of web malefactors and entirely mystified as to their motivation.
Last week several readers notified me that my rss feed on Google Reader was filled with spam (“Order Emsam No RxOrder Emsam Overnight DeliveryOrder… BuyBuy…”).
The strange part was, the feed looked fine when accessed directly on my website or via Bloglines. Only when Google requested the feed did it become corrupted, thus mucking up my content inside Google Reader but not on my website.
(Hat tip to Anthony who diagnosed the ailment: calling curl http://blog.oddhead.com/feed/ yielded clean output, while the same request masquerading as coming from Google, curl -A ‘Feedfetcher-Google; (+http://www.google.com/feedfetcher.html; 10 subscribers; feed-id=12312313123123)’ http://blog.oddhead.com/feed/, yielded the spammed-up version.)
In the meantime, Google Search had apparently deduced that my site was compromised and categorized my blog as spam. Look at the difference between these two searches. Nearly every page containing the query terms, no matter how tangential, takes precedence over blog.oddhead.com in the results. [2009/06/23 Update: This is no longer the case: Apparently Google Search has reconsidered my blog.]
So began a lengthy investigation to find and eradicate the invader. The offending text did not appear anywhere in my WordPress code or database. Argg. I found that my plugins directory was world-writeable: uh oh. Then I found a file named remv.php in my themes directory containing a decidedly un-automattic jumble of code. Apparently this is an especially nasty bugger:
I’ve never seen a hack crop up with the tenacity of “remv.php” tho. Seriously, it’s kind of scary.
I’m still not sure how or even if an attacker used remv.php to corrupt my feed in such a subtle way. I decided on surgery by chainsaw rather than scalpel. I exported all my content into a WordPress XML file, deleted my entire installation of WordPress, reinstalled WordPress, then imported my content back in. I restored my theme and re-entered some meta data, but I still have many ongoing repairs to do like importing my blogroll and other links.
The attack was clever: a virus that sickens but does not kill the patient. The disease left my web site functioning perfectly well, making it less likely for me to notice and harder to track down. The bizarre symptom — corrupting the rss feed but only inside Google Reader — led Chris to wonder if the attacker knew I was a Yahoo! loyalist. That seems unlikely. I don’t think I have enemies who care that much. Also, the spammy feed appeared in Technorati as well. Almost surely I was the victim of an indiscriminate robot attack. Still, after searching around, I couldn’t find another example of exactly this form of RSS feed “selective corruption”: has anyone seen or heard of this attack or can find it? And can anyone explain why?
I also found a bunch of useful WordPress security tips, resources, and plugins that might be useful to others including my future self:
- WordPress, remv.php and you
- 3 must apply security tips for WordPress
- Hardening WordPress
- 5 plugins to keep WordPress secure
- Anatomy of a WordPress hack (“The kicker? All these sites were on Dreamhost.”)
- Did your WordPress site get hacked?
- DreamHost: Troubleshooting hacked sites
- Dealing with a hacker on DreamHost
- Docs on WordPress feeds
- AskApache plugin to display all the internal WordPress URL rewrite rules (example use) (I couldn’t discern how to interpret the output)
- WordPress exploit scanner plugin (I didn’t use after this question spooked me)
- Secure WordPress plugin
- AskApache password protect plugin