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[EOL/EOE] How to enable protection against a Land attack on ScreenOS devices



Article ID: KB26778 KB Last Updated: 08 Apr 2021Version: 3.0

Note: A product listed in this article has either reached hardware End of Life (EOL) OR software End of Engineering (EOE).  Refer to End of Life Products & Milestones for the EOL, EOE, and End of Support (EOS) dates.

This article provides information on how to enable protection against a Land attack on ScreenOS devices.


Understanding Land Attacks

Combining a SYN attack with IP spoofing, a land attack occurs when an attacker sends spoofed SYN packets that contain the IP address of the victim as both the destination and the source IP address.

The receiving system responds by sending the SYN-ACK packet to itself, which creates an empty connection that lasts until the idle timeout value is reached. Flooding a system with such empty connections can overwhelm the system and subsequently causing a denial of service (DoS).

The protection is enabled on a per zone basis. Identify the zone that might face such attacks:

To enable land attack protection via the WebUI, perform the following steps:
  1. Go to Security > Screening > Screen.
  2. Select the required zone.
  3. Enable land attack protection under Deniel of service Defense.
To enable Land attack protection via the CLI, use the following command:
set zone <zone name> screen land
Modification History:
2020-09-16: Article reviewed for accuracy. Minor-non-technical edits.
2021-04-08: Tagged with EOL/EOE.

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