TCP intercept features must be provided by the network device by implementing a filter to rate limit and protect publicly accessible servers from any TCP SYN flood attacks from an outside network.

From Perimeter L3 Switch Security Technical Implementation Guide - Cisco

Part of Routers are not set to intercept TCP SYN attacks

SV-16143r3_rule TCP intercept features must be provided by the network device by implementing a filter to rate limit and protect publicly accessible servers from any TCP SYN flood attacks from an outside network.

Vulnerability discussion

The TCP SYN attack involves transmitting a volume of connections that cannot be completed at the destination. This attack causes the connection queues to fill up, thereby denying service to legitimate TCP users.

Check content

IOS example: ip tcp intercept list 107 access-list 107 permit tcp any 10.10.20.0 0.0.0.15

Fix text

Configure the device to use TCP Intercept to protect against TCP SYN attacks from outside the network.

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