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From André Warnier>
Subject Re: Tomcat access log reveals hack attempt: "HEAD /manager/html HTTP/1.0" 404
Date Tue, 16 Apr 2013 20:10:43 GMT
Pïd stèr wrote:
> On 16 Apr 2013, at 19:38, "André Warnier" <> wrote:
>> Pïd stèr wrote:
>>> On 16 Apr 2013, at 17:58, chris derham <> wrote:
>>>>> Or, another way of looking at this would be that for every 40 servers
>>>>> scanned without a 404 delay, the same bot infrastructure within the same
>>>>> time would only be able to scan 1 server if a 1 s 404 delay was implemented
>>>>> by 50% of the webservers.
>>>> This assumes that the scanning software makes sequential requests.
>>>> Assuming your suggestion was rolled out (which I think is a good idea
>>>> in principal), wouldn't the scanners be updated to make concurrent
>>>> async requests? At which point, you only end up adding 1 second to the
>>>> total original time? Which kind of defeats it.
>>>> Again I'd like to state that I think you are onto a good idea, but the
>>>> other important point is that some (most?) of these scans are run from
>>>> botnets. These have zero cost (well for the bot farmers anyway). My
>>>> point is even if the proposal worked, they don't care if their herd is
>>>> held up a little longer - they are abusing other people
>>>> computers/connections so it doesn't cost them anything directly.
>>>> Sorry but those are my thoughts
>>> I tend to agree. Effort will just be expended elsewhere, and that's
>>> assuming this would have enough of an impact to be noticed.
>> Say that it would be easy to implement this in Tomcat, and that we do not collectively
>> find good reasons not to do so, and that it does get implemented.
>> Then I pledge that my next move would be to bring this similarly onto the Apache
>> list (using the Tomcat precedent as an introduction of course (à la "hey guys ?
>> smart Tomcat developers have just had a great idea etc..")).
>> I haven't checked the actual numbers yet, but I would imagine that between Apache
>> and Tomcat, we're talking of a significant proportion of the overall webservers,
no ?
> Only if you can get them updated in a timely fashion.

I'd say that one has to start somewhere.  Obviously, individually getting in touch with 
each Tomcat sysadmin on the planet is not going to be practical.
But implementing this in the next released version of Tomcat would at least make it so 
that any new installation implements it by default.

> And only if the default setting is 'on'.

That's the idea.  That is one reason why I brought this discussion here : to check if, if

the default factory setting was for example 1000 ms delay for each 404 answer, could 
anyone think of a severe detrimental side-effect ? (other than for the botnet industry of


A drawback of the scheme, for which I do not have a good solution at the moment, is that 
it is a bit like a telephone network : the more people have one, the more useful it 
becomes, and the more will want it.  Conversely, the slower it spreads, the longer it will

take for any effect to be felt. So how could one go about making sure that it spreads as 
quickly as possible ?
That's one problem of open-source/free software : you cannot offer a discount to early 

Incidentally, nobody has commented yet on how easy/difficult it would be to actually 
implement this technically, in an efficient way.

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