[Snort-users] Request for urgent help.

Patrick S. Harper patrick at ...4250...
Mon Aug 21 00:34:01 EDT 2006


I find it amazing that people will beg for help on a public list but not
even use the docs provided on the site of the product they are looking at.
Google is your friend, if you want help on an open source project you can
get it but you have to do some work yourself too.  

-----Original Message-----
From: snort-users-bounces at lists.sourceforge.net
[mailto:snort-users-bounces at lists.sourceforge.net] On Behalf Of Pascal
Charest
Sent: Sunday, August 20, 2006 6:55 PM
To: snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Request for urgent help.

I don't know but.. let's say I was giving out courses on how to deal with
network security and one of the homework is going to be on "how to deploy
snort". That might mean that i'm not totaly a "stucked up academic" (with
only theory), and it might also mean that I follow the development of the
"product" on which I ask question. 

Jeez... I so want to see the day where one of my student (/protégé) is going
to come on here and ask for help by copy/pastig the whole paper ;-).

And I do hope that this guy run in a private email from his teacher! ;-) 

Pascal Ch.


On 8/18/06, Michael Scheidell <scheidell at ...5171...> wrote:

	 

	
	-----Original Message-----
	From: snort-users-bounces at lists.sourceforge.net
[mailto:snort-users-bounces at lists.sourceforge.net] On Behalf Of mark antony
	Sent: Friday, August 18, 2006 1:00 AM
	To: snort-users at lists.sourceforge.net
	Cc: snort-users-admin at lists.sourceforge.net
	Subject: [Snort-users] Request for urgent help.
	
	
	Respected sir
	
	I am am new to use this snort. I have no idea how to use this. I
need some information regarding this question. If i dont do this i am gonna
fail the subject. The university did not provided any guidence on how to use
the snort. I dont know anything. Please some one help me out.
	
	You are a security specialist working for ABC Incorporated.  ABC use
SNORT as their NIDS which protects their IP sub-network being in the range
of 203.40.27.128 – 203.40.27.255.  
	 
	Is it September already?
	
	 

	(a)


	A recent security vulnerability has been found in OpenSSH.  A junior
staff member within the security team developed a new SNORT rule to detect
this attack.  Your supervisor has asked you to check the work of the junior
staff member to ensure there are no errors in the SNORT rule.  
	The security vulnerability is described as follows:
	A buffer overflow has been detected in the OpenSSH server.  Exploits
have been released and exhibit the following characteristics:
	<!--[if !supportLists]-->·         <!--[endif]-->A payload
positioned 100 bytes from the start of the data with a string message "You
are mine" 
	<!--[if !supportLists]-->·         <!--[endif]-->After the above
payload, there is a variable field of 4 bytes specifying a return address.
These 4 bytes can be any value.  
	<!--[if !supportLists]-->·         <!--[endif]-->Following the
variable 4 bytes return address is the exploit code signature given in HEX
as AB 8F 23 8A BC 92
	
	The rule should:
	<!--[if !supportLists]-->·         <!--[endif]-->when triggered,
drop and then log the packet only.
	<!--[if !supportLists]-->·         <!--[endif]-->detect attacks from
inside and outside their private network.
	<!--[if !supportLists]-->·         <!--[endif]-->include a message
with the log entry as "OpenSSH exploit attempt".
	<!--[if !supportLists]-->·         <!--[endif]-->include a reference
to the CVE number CAN-2006-06-3318
	<!--[if !supportLists]-->·         <!--[endif]-->Have a
classification of attempted-admin
	
	
	The rule written by the junior staff member is as follows:
	
	alert udp !203.40.27.0/24 any -> 203.40.27.128/24 23 (msg: "OpenSSH
exploit attempt"; cve:CAN-2006-06-3318; classtype: attempted-admin; content:
"You are mine"; depth: 12; offset:100; content: "AB 8F 23 8A BC 92";
depth:6; offset:4;)
	
	The rule above contains 8 syntax or logic errors.  Your task is to
review the above rule and identify these errors which may prevent the rule
from detecting legitimate attacks, or will cause false positives.  For all
the mistakes, identify the error, explain why it is wrong, and then fix the
error.  
	EXAMPLE:
	Here is a sample rule with a mistake in it.
	alert udp any 53 -> any 53 (msg: "DNS attack"; content: "XYZ";)
	
	Here is an example of the solution format:
	
	Error 1: alert udp any 53 ->
	The source port is given as 53, however requests to a DNS server
from a client will use ephemeral ports, and therefore should be given as
any.  To correct this mistake, the rule should read:
	Solution 1: alert udp any any -> any 53
	
	Make sure to:
	<!--[if !supportLists]-->·         <!--[endif]-->Number each of the
errors you find as shown above (ie. Error 1)
	<!--[if !supportLists]-->·         <!--[endif]-->Provide a copy of
the portion of the rule which contains the error.  Be sure to include
keywords around the error to make it clear which part of the rule you are
referring to.  If you prefer, for each error, re-write the entire rule and
highlight the error (see next point)
	<!--[if !supportLists]-->·         <!--[endif]-->Highlight in some
way the specific part of the rule you are referring.  In the example above,
the source port number "53" was underlined.  If you do not make it clear
which part of the rule is incorrect, no marks can be given.  
	<!--[if !supportLists]-->·         <!--[endif]-->Be sure to include
a clear explanation of why the rule was wrong and how it should be fixed
	<!--[if !supportLists]-->·         <!--[endif]-->Re-write the
portion of the rule again with the correction included and highlighted (ie
underlined)
	
	
	MARKING CRITERIA:
	Each correctly identified error with a clear explanation and a
correct fix for the error will be assigned a ¼ mark.  No part marks will be
assigned, so if you correctly identify the error, but do not provide an
appropriate fix or your explanation of the error is vague or incorrect, no
marks will be assigned.

	(b)
(4 marks)

	Your supervisor asks you to implement a SNORT IDS rule to detect and
alert all attempts at exploiting the vulnerability as described below for
any computer on the internal network.  He then asks you to write an
explanation of each component of the rule, so other security specialists in
your team can see how your rule is written.  The rule should notify the
security team when an attempt is made using the message: "NEW PING O' DEATH
EXPLOIT ATTEMPT".  Be sure to allocate an appropriate sid value and a
revision number for your new rule, the appropriate class type for this
attack, and that you include the appropriate CVE id and a nessus
vulnerability scanner id as described below. 
	
	A new atomic denial of service attack has been discovered.  It
behaves similarly to the Ping o' death exploit that caused great chaos many
years ago – once the victim's computer receives the exploit packet, it will
immediately crash.  Thus, it has been named "New Ping o' Death" and has a
CVE of "2006-0721" and nessus id of "21091".  The attack is a single ping
request with an invalid code field.  Current variants of the exploit have
been using a code field value of '1001' (expressed here in binary), however
your rule should detect all ping requests with an invalid code field value.
Furthermore, to exploit the vulnerability the type of service value should
be set to "Minimise delay".  
	
	
	An example of how to layout your solution follows:
	
	var HOME_NET 138.77.23.0/16
	var EXTERNAL_NET !138.77.23.0/16
	Your explanation of the above in italics
	drop udp $EXTERNAL_NET any -> $HOME_NET 993
	Your explanation of the above, and so on

	
	An example explanation for a SNORT rule option:
	content: "USER root"; nocase;
	The content of the packet must contain the string "USER root" to be
matched.  Furthermore, the nocase option specifies that the string "USER
root" should be matched case insensitively.  In other words, it will match
that string whether in upper, lower or mixed capitalisation.


	

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-- 
Pascal Charest, Feydakin
http://blog.pacharest.com
-- 






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