Drop Code: 70(Invalid TCP Flag(#1))

07/21/2023 47 People found this article helpful 425,540 Views

Description

When the URG flag is set on a TCP stream, the firewall will drop packets with Drop Code: 70(Invalid TCP Flag(#1)), Module Id: 25. This is set by default as a security measure to prevent attacks like TCP X-mas, DOS, DDOS, etc.

Cause

The firewall will drop the TCP packets with URG flags by default to prevent any forms of attacks similar to DOS, DDOS, TCP-Xmas, etc.

Resolution

Resolution for SonicOS 7.X

This release includes significant user interface changes and many new features that are different from the SonicOS 6.5 and earlier firmware. The below resolution is for customers using SonicOS 7.X firmware.

Navigate to Policy | Rules and Policies | Access Rules
Select the access rule in question which will define the traffic flow and click on the edit
Navigate to Optional Settings | Allow TCP URG packets
Enable the check box and save the settings.

Resolution for SonicOS 6.5

This release includes significant user interface changes and many new features that are different from the SonicOS 6.2 and earlier firmware. The below resolution is for customers using SonicOS 6.5 firmware.

Navigate to Manage | Rules | Access Rules
Select the access rule in question which will define the traffic flow and click on the edit
Navigate to Advanced | Allow TCP URG packets
Enable the check box and save the settings