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 actually 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.

How it works

The attack involves sending a spoofed TCP SYN packet (connection initiation) with the target host's IP address and an open port as both source and destination.

The reason a LAND attack works is because it causes the machine to reply to itself continuously.

Definition: "A LAND attack involves IP packets where the source and destination address are set to address the same device."

Other land attacks have since been found in services like SNMP and Windows 88/tcp (kerberos/global services) which were caused by design flaws where the devices accepted requests on the wire appearing to be from themselves and causing replies repeatedly.

Vulnerable systems

Below is a list of vulnerable operating systems (discovered by testing on various machines):^{[citation needed]}

• AIX 3.0
• AmigaOS AmiTCP 4.2 (Kickstart 3.0)
• BeOS Preview release 2 PowerMac
• BSDi 2.0 and 2.1
• Digital VMS
• FreeBSD 2.2.5-RELEASE and 3.0 (Fixed after required updates)
• HP External JetDirect Print Servers
• IBM AS/400 OS7400 3.7
• Irix 5.2 and 5.3
• Mac OS MacTCP, 7.6.1 OpenTransport 1.1.2 and 8.0
• NetApp NFS server 4.1d and 4.3
• NetBSD 1.1 to 1.3 (Fixed after required updates)
• NeXTSTEP 3.0 and 3.1
• Novell 4.11
• OpenVMS 7.1 with UCX 4.1-7
• QNX 4.24
• Rhapsody Developer Release
• SCO OpenServer 5.0.2 SMP, 5.0.4
• SCO Unixware 2.1.1 and 2.1.2
• SunOS 4.1.3 and 4.1.4
• Windows 95, NT and XP SP2

How to avoid being attacked

Most firewalls should intercept the poison packet thus protecting the host from this attack. Some operating systems released updates fixing this security hole.

External links

• Insecure.Org's original post about the attack
• Article about XP's vulnerability