[Snort-sigs] Couple sigs

Alex Kirk akirk at ...435...
Mon Sep 10 09:52:53 EDT 2012


With, that is, some tweaks to be slightly less specific. If you can be
evaded by simply switching the order of the width and height on the first
one, for example, well, you're probably less than useful.

(Sorry for clogging anyone's inbox with a second mail here, it's still
early on a Monday morning.)

On Mon, Sep 10, 2012 at 9:49 AM, Alex Kirk <akirk at ...435...> wrote:

> These look like solid rules, James - especially the hidden Iframe bit,
> that seems like suspicious practice even if it's on a "legit" web site.
>
> I'm going to have these run through our rule testing group, just in case
> we see legit sites doing either one of these things on a regular basis -
> but assuming that they come up clean, I think they'd be excellent additions
> to, say, INDICATOR-OBFUSCATION.
>
>
> On Fri, Sep 7, 2012 at 2:06 PM, James Lay <jlay at ...3266...>wrote:
>
>> So...I get really tired of malicious redirects, so here are a couple
>> sigs:
>>
>> Maybe hidden iframes are all over the net...maybe not, but this one is
>> specifically designed to catch stuff like the below:
>>
>> alert tcp $EXTERNAL_NET $HTTP_PORTS -> $HOME_NET any (msg:"WEB-CLIENT
>> Hidden iframe"; flow:to_client, established; file_data; content:"<iframe
>> width=1 height=1 style=visibility|3a|hidden"; classtype:bad-unknown;
>> sid:10000023; rev:1;)
>>
>> <iframe width=1 height=1 style=visibility:hidden
>> src='http://www.redacted.com/wp-count.php?ref=redacted</iframe>
>>
>>
>>
>>
>> this next one is to catch those pages that are just a single refresh
>> line with a link to an IP...I see a lot of these types being pointed at
>> from compromised (wordpess) sites...as I understand it file_data should
>> make this sig search from the beginning of the response body...which is
>> exactly where I want it to search and not say the middle of the page (I
>> hope):
>>
>>
>> alert tcp $EXTERNAL_NET $HTTP_PORTS -> $HOME_NET any
>> (msg:"INDICATOR-COMPROMISE Page with only IP redirect, possible
>> compromised site"; flow:to_client, established; file_data;
>> content:"<html><head><meta http-equiv=|22|refresh";
>> pcre:"/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/sm"; classtype:bad-unknown;
>> sid:10000024; rev:1;)
>>
>> <html><head><meta http-equiv="refresh"
>> content="0;url=http://redacted/redacted"></meta></head></html>
>>
>>
>>
>>
>> So far no FP's in my environment, your mileage may vary.  As usual,
>> comments, thoughts, improvements, hack & slash on these are welcome.
>> Thanks all.
>>
>> James
>>
>>
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>>
>
>
>
> --
> Alex Kirk
> AEGIS Program Lead
> Sourcefire Vulnerability Research Team
> +1-410-423-1937
> alex.kirk at ...435...
>



-- 
Alex Kirk
AEGIS Program Lead
Sourcefire Vulnerability Research Team
+1-410-423-1937
alex.kirk at ...435...
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