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Re: Couple sigs

From: Alex Kirk <akirk () sourcefire com>
Date: Mon, 10 Sep 2012 09:49:57 -0400
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 () slave-tothe-box net> 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 () sourcefire com

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Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
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