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nuecaster
Asked: 2011-05-18 12:17:05 +0800 CST

1 user, 1 day, millions of requests for the same file

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Help!

Here's the scenario:

I'm hosting and serving display ads. These consist of some media creatives and some javascript files to assemble and display the ad. The files are hosted on a CDN.

We did a small test run with 1 ad over the weekend. It burned about 10,000 impressions. When reviewing my CDN logs, I notice that one single IP, was requesting a single media file, on average about 2-3 times per second to the tune of over 1.6 million hits on the file. All in within a 24 hour period!

Now this is a big problem because I'm charged for bandwidth, and currently we've transferred over a TB for no apparent reason.

Why is this happening?? What can I do to prevent anything from accessing files directly like this? They should only be accessed when the javascript calls them into an ad placement.

Lines from CDN log:

#Fields: timestamp time-taken c-ip filesize s-ip s-port sc-status sc-bytes cs-method cs-uri-stem - rs-duration rs-bytes c-referrer c-user-agent customer-id x-ec_custom-1
1305405902 116 XX.XX.XX.XX 1281559 XX.XX.XX.XX 80 TCP_HIT/200 327990 GET http://XXXXXXXXXX.ogg - 0 557 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 ( .NET CLR 3.5.30729)" 10629 "-" 
1305405902 89 XX.XX.XX.XX 1281559 XX.XX.XX.XX 80 TCP_HIT/200 655670 GET http://XXXXXXXXXX.ogg - 0 557 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 ( .NET CLR 3.5.30729)" 10629 "-"
1305405902 86 XX.XX.XX.XX 1281559 XX.XX.XX.XX 80 TCP_HIT/200 453386 GET http://XXXXXXXXXX.ogg - 0 557 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 ( .NET CLR 3.5.30729)" 10629 "-"
1305405902 7 XX.XX.XX.XX 1281559 XX.XX.XX.XX 80 TCP_HIT/200 1281869 GET http://XXXXXXXXXX.ogg - 0 557 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 ( .NET CLR 3.5.30729)" 10629 "-"
1305405903 86 XX.XX.XX.XX 1281559 XX.XX.XX.XX 80 TCP_HIT/200 786742 GET http://XXXXXXXXXX.ogg - 0 557 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 ( .NET CLR 3.5.30729)" 10629 "-"
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2 Answers

  1. You could...

    Set the expiration header on the http response...

    Since you don't mention the CDN I don't know how they will let you influence that. They might be making big bucks off poor client by not allowing it :) In that case, run, don't walk, to a CDN that will allow it

    http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.21

    Edit A single IP? You did run whois yet... Perhaps you can contact the abuse contact from there

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  2. I've seen this before (ironically enough, with an ad network I was once contracted to) -- they had a bug in their Javascript that (under certain, rare-but-not-unknown circumstances) caused the client to head into an infinite loop and continuously attempt to retrieve ads. They were running pretty close to the limits of their hosting infrastructure already, and doing 80+million impressions a day, so it only took a small percentage of misbehaving clients to cause some serious damage to their uptime -- it was effectively a self-imposed DDoS. The devs fixed that bug real quick, but it took a couple of days for the last misbehaving client to go away (people leave their browsers open for a lot longer than I would have expected).

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