[Snort-users] Request for urgent help.

Pascal Charest pascal.charest at ...11827...
Sun Aug 20 19:54:32 EDT 2006


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