revival – #2

These posts republish content from the now defunct site. The following one is a very good one, by somebody who knows networking: Martin Roesch, the author and lead developer of Snort.

Dissecting GRC’s

by martin.roesch

refer to :

so in the “broken out” packet dump at the bottom of the page, he’s
got several errors.

  1. The TCP offset
    (TCP header length) is set to 6, which means that the TCP header
    length should be 24, and the packet shown only has a 20 byte header.
  2. The Sequence
    number is 0, which should never happen on a SYN packet and would
    be easily picked up by any intrusion detection system (like Snort).
  3. The IP datagram
    length field shows 44-bytes, but once again we’re only shown 40-bytes.
    Where’d those other 4 bytes go?

Beyond that, this
is a standard SYN packet, hardly revolutionary.

The packet at
the top is a simple ICMP ECHO packet (ping), which is presumably
being filtered at the NSA’s gateway.  That’s why a response
has “never been received”… Ooh, spooky!

The other claims
are so much fluff.  Temporal density?  Just because the
packet’s got half as many bits as the equivalent ECHO packet
from MS doesn’t mean that the extra nanosecond saved is going to
be added onto your life.

These packet’s
aren’t stealthed by any measure, they’re only stealthed to the uninitiated
because most peoples eyes glaze over when confronted with binary
data.  What we’ve been presented with is a an ICMP ECHO packet
and a TCP SYN packet.

Let’s look at
the other claims:

“While you
wait, real-time operation”

Explanation: When you execute the program, it runs and
reports back to you.

host-presence verification”

Explanation: When you run the scan, it pings the target
to make sure it’s up.  Contrary to the claims on the web
page, every other scanner under the sun that’s used for any large
scale application (like nmap, CyberCop, ISS, etc) does this.

host IP address determination”

Explanation: Resolves DNS names, can make other DNS queries.

“Host stealth
technology detection, penetration, and appraisal”

Explanation: If the host is discovered, it will be scanned!
 If the host can be reached through the firewall, it’ll also
be scanned.  If the firewall is filtering the traffic, the
program will attempt to get through but probably won’t unless
some well known vulnerability can be exploited.

“True firewall,
versus simple packet filter, discrimination”

Explanation: They see if their packets are rejected outright
or if some sort of connection establishment is allowed.

“Half-Open” TCP connection “SYN” probing”

Explanation: This was special about four years ago, but
now it’s just called a SYN scan.  This is different than
a full SYN scan in that the connection is dropped after
receiving the returned SYN-ACK packet instead of letting the connection
complete.  This is different from a free port scanner like
nmap in exactly 0 ways.

TCP non-connection “ACK” probing”

Explanation: They can do ACK scans as well.   This
is completely revoloutionary unless you’ve used almost any other
free scanner in the past four years.

and reordered packet filtering vulnerability assessment

Explanation: nmap + fragrouter = this capability, plus

reflection response probing”

Explanation: If you send a properly formatted UDP packet
to port 137 on MS boxen that allow it, you’ll get a response back.
 If it’s not available, you’ll get an ICMP UNREACHABLE.  My
god, the amazing powers of this software aren’t to be believed!!

source IP analysis”

Explanation: IP spoofing! Revolutionary! Nmap has only
had this capability for (at least) four years, but these guys
have made it revolutionary by sticking it in their product to
jack with badly misconfigured firewalls.  Amazing!

Router vulnerability assessment”

Explanation: If you’re behind a NAT, there’s a chance that
the nanoprobe may notice!

Router vulnerability assessment”

Explanation: If your router/NAT is badly misconfigured,
a nanoprobe may be able to see some of the other addresses that
the thing is configured to talk to.

protocol testing”

Explanation: Application layer testing, such as trying
to brute force passwords on SMB shares.  This has never been
done before, unless of course you count the NetBIOS Auditing Tool
(nat) program from the mid 90s…

round trip time (RTT) profiling”

Explanation: This is useful if you’re trying to see if
there’s any time based elements to see if you’re talking to a
firewall or directly to the host.  Righteous.

spoof proof”

Explanation: “We can’t be spoofed because we make our own
packets!”   What about man in the middle attacks guys?  Are
you talking IPv6 or over an encrypted tunnel?  No?  Oops,
you can be spoofed.

Anybody remember
the FreeVeracity BS from a few weeks back?  I smell repeat!
There’s no magic here, other than the fact that this got posted
to Slashdot at all.

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