Robotic Tendencies
The personal blog of Robert McQueen

October 19, 2005


Just a quick post to reply to the comments I’ve had on some previous posts.

On Missing entropy on my server box, I received lots of comments on how to feed random other stuff into the entropy pool or make it bigger or other hacks, but Alexander Reelsen pointed me to the real cause — a kernel bug in older 2.4 kernels which causes the entropy pool to deadlock on SMP systems, and never get refilled. There is a patch from RedHat which backports the fix from 2.6, and is included in recent 2.4 kernels.

On the topic of kernels, now I’ve upgraded from 2.4.29-rc1 to 2.4.32-rc1 I get lots of errors like hw tcp v4 csum failed in my syslog. I’m using the e100 driver which as far as I can see hasn’t changed between versions, but there have been some changes to TCP checksumming code which I havn’t quite been able to grok. Google finds mailing list posts with other people asking what the cause is, but nobody answering. Anyone know what’s going on there?

On Windows accessibility, many people seem to not listened to the first couple of minutes of the tasteless song I linked to, and hence taken my comment completely seriously. Thanks to everyone who told me about sticky keys etc in comments, but I did already know about the existence of Windows accessibility support (warning: mjg59 in furious anger mode). 😀

On the topic of blog comments, how do I cut down on the comment spam I have to moderate without requiring people to go through a completely unaccessible captcha image thing, or the annoyance of registering and acknowledging an e-mail? Would prohibiting comments and URIs containing words like ‘mortgage’, ‘casino’ and ‘ringtone’ ever cause false positives?

posted by ramcq @ 12:55 pm
Comments (6) .:. Trackback .:. Permalink

6 responses to “Comments”

  1. Rob Caskey says:

    You are not special to spammers: a simple “Type the word Cow in the following box” would be enough to stop them.

  2. sb says:

    Yes, there’s a very good chance that a legitimate comment would contain the word “casino”. Like this one, for instance.

    One technique that I’ve seen is to include extra fields that a bot doesn’t know how to fill out (“time zone” maybe), or extra buttons that it doesn’t know how to click. Using JavaScript is good because few bots are smart enough to speak it.

    Of course, the specifics are something that you should come up with on your own. If it gets too popular, someone will write a bot for it.

  3. Anonymous says:

    I’ve heard good things about wp-hashcash.

  4. Brian says:

    Spam Karma 2 (WP plugin) is easily the best solution I’ve tried. Seems to catch all my spam (close to 100 per day) without any false positives so far. I think I have it on the default settings, even.

  5. Erik Harrison says:

    Several of us Xfce devs have found that Spam Karma 2 is just about the nicest anti blogspam tool we’ve used

    It’s pretty clever about picking between spam and ham, using multiple tests and giving messages a spam rating. An additional nicity is the lack of a captcha requirement by default – captcha only gets used in cases where the post is ambiguously spam. Obvious spam just gets dropped, obvious ham never sees the captcha.

  6. mathrick says:

    Depends on what blog system you use, but I’ve just upgraded mine to WP 1.5 and installed Spam Karma 2 — so far it’s working wonders, no spam gets through, while it’s hard (I tried and failed) to get your comment moderated when typing it in by hand. I don’t know how well it plays with text-mode browsers, though, using JScript payload and captcha for ambigous ones.

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