Detections
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1.18 CISC-RT-000310

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Information

The Cisco perimeter switch must be configured to restrict it from accepting outbound IP packets that contain an illegitimate address in the source address field via egress filter or by enabling Unicast Reverse Path Forwarding (uRPF).

GROUP ID: V-221091
RULE ID: SV-221091r999700

A compromised host in an enclave can be used by a malicious platform to launch cyberattacks on third parties. This is a common practice in "botnets", which are a collection of compromised computers using malware to attack other computers or networks. DDoS attacks frequently leverage IP source address spoofing to send packets to multiple hosts that in turn will then send return traffic to the hosts with the IP addresses that were forged. This can generate significant amounts of traffic. Therefore, protection measures to counteract IP source address spoofing must be taken. When uRPF is enabled in strict mode, the packet must be received on the interface that the device would use to forward the return packet, thereby mitigating IP source address spoofing.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

Configure the switch to ensure that an egress ACL or uRPF is configured on internal interfaces to restrict the switch from accepting any outbound IP packet that contains an illegitimate address in the source field. The example below enables uRPF.

SW1(config)# int e2/4
SW1(config-if)# ip verify unicast source reachable-via rx
SW1(config-if)# end

See Also

https://workbench.cisecurity.org/benchmarks/22581

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5(1), CAT|I, CSCv7|14.6, Rule-ID|SV-221091r999700_rule, STIG-ID|CISC-RT-000310, Vuln-ID|V-221091

Plugin: Cisco

Control ID: 8ae36556a7a66afb1d8a0f2ee9564631263646e8652a20498144f9ed702fd75e