The router 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.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-55761	SRG-NET-000026-RTR-000031	SV-70015r1_rule		Medium

Description
A compromised host in an enclave can be used by a malicious actor as a platform to launch cyber attacks on third parties. This is a common practice in "botnets", which are a collection of compromised computers using malware to attack (usually DDoS) other computers or networks. DDoS attacks frequently leverage IP source address spoofing, in which packets with false source IP addresses send traffic to multiple hosts, which then send return traffic to the hosts with the IP addresses that were forged. This can generate significant, even massive, amounts of traffic. Therefore, protection measures to counteract IP source address spoofing must be taken. The router must not accept any outbound IP packets that contain an illegitimate address in the source address field by enabling Unicast Reverse Path Forwarding (uRPF) strict mode or by implementing an egress ACL. Unicast Reverse Path Forwarding (uRPF) provides an IP address spoof protection capability. 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.

Description

A compromised host in an enclave can be used by a malicious actor as a platform to launch cyber attacks on third parties. This is a common practice in "botnets", which are a collection of compromised computers using malware to attack (usually DDoS) other computers or networks. DDoS attacks frequently leverage IP source address spoofing, in which packets with false source IP addresses send traffic to multiple hosts, which then send return traffic to the hosts with the IP addresses that were forged. This can generate significant, even massive, amounts of traffic. Therefore, protection measures to counteract IP source address spoofing must be taken. The router must not accept any outbound IP packets that contain an illegitimate address in the source address field by enabling Unicast Reverse Path Forwarding (uRPF) strict mode or by implementing an egress ACL. Unicast Reverse Path Forwarding (uRPF) provides an IP address spoof protection capability. 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.

STIG	Date
Router Security Requirements Guide	2016-07-01

Details

Check Text ( C-56327r2_chk )
Review the router configuration to verify uRPF or an egress filter to restrict the router from accepting outbound IP packets that contain an illegitimate address in the source address field has been configured on all internal interfaces. If uRPF or an egress filter to restrict the router from accepting outbound IP packets that contain an illegitimate address in the source address field has not been configured on all internal interfaces in an enclave, this is a finding.

Check Text ( C-56327r2_chk )

Review the router configuration to verify uRPF or an egress filter to restrict the router from accepting outbound IP packets that contain an illegitimate address in the source address field has been configured on all internal interfaces.

If uRPF or an egress filter to restrict the router from accepting outbound IP packets that contain an illegitimate address in the source address field has not been configured on all internal interfaces in an enclave, this is a finding.

Fix Text (F-60631r1_fix)
Configure the router to ensure that an egress filter or uRPF is configured to restrict the router from accepting any outbound IP packet that contains an external IP address in the source field.