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RE: RLA ("Remote LanD Attack")
From: "Roger A. Grimes" <roger () banneretcs com>
Date: Thu, 15 Dec 2005 13:46:37 -0500

Just to clarify, so that people don't think this affects Windows XP SP2.
I've tested SP2 again, and the LAND attack no longer works. This
announcement concerns gateway network devices that computers may attach
to (the announcement is a little confusing at first).

Also, to pull off the hping2 example, you'll need the -k parameter to
make sure the source port stays at port 80, else it will increment up
(80, 81, 82, etc.)


*Roger A. Grimes, Banneret Computer Security, Consultant 
*CPA, CISSP, MCSE: Security (2000/2003/MVP), CEH, yada...yada...
*email: roger () banneretcs com
*Author of Honeypots for Windows (Apress)

-----Original Message-----
From: Synister Syntax [mailto:synistersyntaxlist () gmail com] 
Sent: Wednesday, December 14, 2005 1:49 AM
To: bugtraq () securityfocus com; full-disclosure () lists grok org uk;
vuln-dev () securityfocus com; NTBUGTRAQ () listserv ntbugtraq com
Subject: RLA ("Remote LanD Attack")

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



("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

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

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

- 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

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