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Re: RLA ("Remote LanD Attack")
From: Synister Syntax <synistersyntaxlist () gmail com>
Date: Thu, 15 Dec 2005 10:56:11 -0500

     I agree that this is in fact a DoS, however it is using the old
LanD attack (from 1997) syntax/style.  That fact that it is a packet
to itself, from it's self, obviously spoofed.  As this was the same
way it was done back in the 90's.  The difference here, is the fact
that the LanD attack can be performed remotely, whereas before the
attack was only a Local (LAN) attack.

     Also note that this is an attack on devices, not OS's.  Also let
me note that the device is unusable until it is physically reset. 
Eitherway, I am fine by this being consedered a DoS, it is.  It will
shut doen your switch (rendering your network usaless) or your router
(keeping you from access the internet etc.).

If you have any other questions, or comments please let me know. 
Thanks for the input, I think I did infact not state that the attack
was a DoS.

On 12/15/05, service pack <sppride () gmail com> wrote:
Updated the wiki page. Your looking at a denial of service not a land

 Land attacks are caused when a machine floods itself.

 First example,  Echo and Chargen (ICMP and Character generator (old unix
service)) Are services that reply to anything.
 A spoofed packet is sent from a machines echo (spoofed) to the chargen. The
chargen replys with garbage, and the echo echo's it
 back and so on until the resources are consumed.

 Anything that doesn't have this effect is a Denial of service.

 Now SNMP and windows Kerberos can talk themselves to death (an example of a
non-cross service land).

 Makes sense? :)


On 12/14/05, Synister Syntax <synistersyntaxlist () gmail com> wrote:
Below is a copy of my RLA exploit submission in ASCII.  Attached is a
MSWord (.doc) version with rich formatting, created with ease of view
in mind.



("Remote LanD Attack")

As discovered by:
Justin M. Wray
(jayizkool () gmail com)

Devices/Vendors Vulnerable:
- Microsoft Windows XP, SP1 and SP2
- Linksys Routers
- Westell Routers/Modems
- Motorola Modems/Routers
- Cisco Firewalls, Switches, and Routers
- DSL Modems
- Cable Modems
- Consumer Routers
- All Central Connectivity Devices (any manufacturer)

Devices/Vendors Tested:
- Linksys BEFW11S4
- Linksys WRT54GS
- Westell  Versalink 327W (Verizon Modem)
- Cisco Catalyst Series (Multiple)
- Scientific Atlantic DPX2100 (Comcast Modem)

A LAND attack is a DoS (Denial of Service) attack that consists of
sending a special poison spoofed packet to a computer, causing it to
lock up. The security flaw was first discovered in 1997 by someone
using the alias "m3lt", and has resurfaced many years later in
operating systems such as Windows Server 2003 and Windows XP SP2.

Explanation of LanD:
LanD uses a specially crafted ICMP  echo packet which has the same
source and destination address.  The receiving system stalls due to
the erroneous packet and not having instructions to handle the unique
packet.  In Windows 9x  variants, the systems will "blue screen. "  On
modern NT  variants, the systems will hang for approximately 30
seconds with full CPU usage before discarding the packet.  With a
looped script, the attacker can render the system useless.  UNIX
variants have been able to use a firewall rule to drop LanD packets –
leaving most systems patched.

Microsoft originally released an initial patch that secured Windows 9x
variants – causing the exploit to lose popularity and become somewhat
obscure.  Later, when Windows NT variants were released, Microsoft
neglected to patch the security flaw; this caused Windows XP Service
Pack 2 to remain susceptible to such an attack.  Within the last four
(4) months, Microsoft has released a patch for Windows NT variants.

LanD versus Remote LanD:
LanD was originally introduced in the late 1990s and was very popular
with educational and business networks.  The original LanD attack had
to be executed internally on the local network – thereby giving rise
to the name "LanD" (indicating that access has been granted to the
local premises).  However, with a remote attack (Remote LanD),
crafting special packets and spoofing the destination and source IP
addresses will cause the attack to be carried out remotely against the
central connectivity device.

Exploit / Proof of Concept:
There is no handwritten code needed to exploit this vulnerability.
The only requirement is an IP packet creation utility (such as HPing2
or IPSorcery). Below are some HPing2 examples:
                Victim's IP Address:
                Victim's Router IP Address:
                hping2 -A -S -P -U -s 80 -p 80 -a

Remote LanD Specifications:
Although the exploit will work without the Ack, Syn, Push, and Urg
(flags), the device does not seem to shut off without these flags.
Sending just the LanD part of the packet seems to only create high
amounts of latency on the victim's end.  The spoofed source address
must be the address of the central connectivity device; although the
normal default is, some manufacturers use different
addresses (such as or  As a result, the IP
address should be checked prior to initiating any test.  Additionally,
a broadcast address will work for a source address as well, thereby
flooding the network with responses from all the machines connected to
the network.  Although it will not stale the Central Connectivity
Device, it will maximize the entire network usage - crippling the
network with extremely high latency.

Test Environment:

- Test One
  - Attacker:  hping2 on Comcast Cable connection behind Linksys Router
  - Victim:  DSL Modem/Router on Verizon DSL connection

- Test Two
  - Attacker:  hping2 on Comcast Cable connection behind Linksys Router
  - Victim:  Linksys Router on Comcast Cable connection

- Test Three
  - Attacker:  hping2 on Comcast connection behind Linksys Router
  - Victim:  Comcast Cable Modem

- Test Four
  - Attacker:  hping2 on Comcast connection behind Linksys Router
  - Victim:  Cisco Router on T1 connection

- Test Five
  - Attacker:  hping2 on Comcast connection behind Linksys Router
  - Victim:  Cisco Pix Firewall, on T1 connection

Test Results:

Test One:
Connection Latency - followed by the modem physically turning off.
Time elapsed: approximately 10 seconds (from beginning of packet
flooding to complete shutdown).

Test Two:
Connection Latency, router reset, then connection lost.  Reset needed
before router would communicate online again.

Test Three:
Modem lights flickered; the modem lost connection and sat with the
Data light completely out.

Test Four:
Router lost connection to the internet.

Test Five:
Firewall lost network connection.
It appears that central connectivity device manufacturers need to
release firmware updates and/or patches to protect against LanD and
remote LanD attacks. The LanD attack is no longer simply a local
attack but has now evolved into having the capability of being
launched remotely.

- Casey O'Brien, M.S.
  - Assisted with test trials
- Matthew Wines
  - Assisted with test trials
- Yvonne M. Wray, M.S.
  - Report editor

Submitted: 12/14/2005 by Justin M. Wray

Netowork Manager, Server Administrator, Security Specialist
( http://www.teamtrinix.com)


Netowork Manager, Server Administrator, Security Specialist

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