Snort mailing list archives

Re: Request for urgent help.


From: "Pascal Charest" <pascal.charest () gmail com>
Date: Sun, 20 Aug 2006 19:54:32 -0400

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 () secnap net> wrote:



 -----Original Message-----
*From:* snort-users-bounces () lists sourceforge net [mailto:
snort-users-bounces () lists sourceforge net] *On Behalf Of *mark antony
*Sent:* Friday, August 18, 2006 1:00 AM
*To:* snort-users () lists sourceforge net
*Cc:* snort-users-admin () 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
--
-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Snort-users mailing list
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