Kurt Seifried wrote:
>>On Tue, Jul 08, 2003 at 11:38:58PM -0700, Kurt Seifried wrote:
>>
>>>typically are just banner harvesting tools (i.e. Nessus) and not actually
>>>"exploit the service, and run shell code on the remote end".
>>
>>I won't reply to the list, but this is a gross mis-statement.
>>
>>-- Renaud
>
>
> I have to agree and I apologize, it was late and I couldn't think of another
> example quickly. The basic issue however reamins that the majority of pen
> testing tools do not actually break into the server, they typically harvest
> a banner ("Sendmail 8.foo, you got bugs!") which can cuase them to spew if
> you're like me and have Bind report binary junk data to version requests
> (which causes a lot of pen testing tools to choke) or they execute part of
> the attack (i.e. cause an error message, whatever). Nessus does have the
> denial of service tests, however last I checked none of the tests will
> actually give you a remote shell (although they could be could be modified
> to do so but then you're back to basically writing all your exploits from
> scratch).
>
Having worked in the development team a vuln scanner in a previous life I
concur that banner grabbing is just the simplest way of attempting to verify
the presence of a vulnerability and not a very accurate one. Nessus as well
as most vuln scanners do *much more* than just that and its not always easy
to correctly identify a vulnerability without doing some sort of 'active
testing' although not necessarily exploiting it to gain access to the host.
CVE-1999-0493 "Solaris rpc.statd Call Relying vulnerability" is an example
of the complexity involved in just *checking* for a vulnerability.
In this case to remotely check for the vulnerability, rpc.statd must be
fed with some specific data that overwrites internal structures, then
it must be forced to interact with other RPC services on the target host
and generally there will be no response to check for, so the tester needs
to do something to verify sucess (write a file to the file system, send
a packet back to the scanner, etc.), this is some sort of active testing or
at least involves a 'degree of exploitation'. Still trying to actually
exploit a vulnerability to gain access to the host and to do so in a
reliable way that works with a wide range of OS versions, patchlevels and
configuration settings *adds even more complexity* to the already complex
problem of testing for vulns. It does have some advantages tho.
Namely, the ratio of false positives diminishes quickly and if the exploits
are good enough the ratio of false negatives should decrease as well, or
at least should mimic the *real* risk level of an attacker as capable as the
developer of the exploit.
-ivan
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