As you know, Subtext actually uses ReverseDOS integration to fight spam.
ReverseDOS is a very simple HttpModule that checks various parts of incoming requests against a list of spam filters that you set. If ReverseDOS detects a match with the filters, it attempts to stall the requesting client for a number of seconds (specified in a .config file).
The facts:
- after the last trackback's spam attack to my blog, I've updated the ReverseDOS.config configuration. It was thursday evening.
- Friday morning I try to open my blog page and it doesn't respond: the favicon was loaded on the browser but the page content was not showed. I was thinking to a problem on the server, so...wait...
- Friday afternoon, I try to reopen the blog's page: always the same story, no content was showed. I decide to go to my IIS configuration and check for problems. All was good.
- Friday evening, the same... I decide to check also for problems on the database by executing the stored procedures manually, but all was good. The web.config was good too...
- This morning, the problem was the same... I decide to install another instance of Subtext to test for server's problem: all was good, the new istance was working correctly with the old database. Now, a light appears on my mind... maybe the updated ReverseDOS.config file is the cause of the problem?
- I open the new ReverseDOS.config (where I've added custom filters in the past days) and I remove the last inserted filter between the tags <filter isRegex="true"> ... </filter>.
- I upload the new ReverseDOS.config on the old application and try to execute it: all was good, magically my blog's content is appeared!
So, what was the problem? I don't know well how ReverseDOS works internally, but the filter part that cause the problem was this:
<filter isRegex="true">hotel|hotels</filter>
By removing the plural name (leaving only <filter isRegex="true">hotel</filter> all was good.
Why ReverseDOS blocks the blog's content in this case? A loop on my mind when I wrote this spam filter and (maybe) a loop also on the ReverseDOS engine... 