Internet Control Message Types (ICMP) must be blocked outbound to external untrusted networks (e.g., ISP and other non-DoD networks).

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-3027	NET0912	SV-15369r2_rule	ECSC-1	Medium

Description
Using ICMP messages for information gathering is a process allowing malicious computer attackers to launch attacks against a targeted network. In this stage the malicious attacker will try to determine what the characteristics of the targeted network. Techniques, such as host detection, service detection, network topology mapping, and operating system fingerprinting are often used. The data collected will be used to identify those hosts running network services, which may have a known vulnerability. This vulnerability may allow the malicious attacker to exploit vulnerabilities in the network or gain unauthorized access to those systems. This unauthorized access may become the focal point to the whole targeted network.

Description

Using ICMP messages for information gathering is a process allowing malicious computer attackers to launch attacks against a targeted network. In this stage the malicious attacker will try to determine what the characteristics of the targeted network. Techniques, such as host detection, service detection, network topology mapping, and operating system fingerprinting are often used. The data collected will be used to identify those hosts running network services, which may have a known vulnerability. This vulnerability may allow the malicious attacker to exploit vulnerabilities in the network or gain unauthorized access to those systems. This unauthorized access may become the focal point to the whole targeted network.

STIG	Date
Perimeter Router Security Technical Implementation Guide Juniper	2017-12-07

Details

Check Text ( C-12836r2_chk )
Review ACLs configured on network devices connected to untrusted networks (e.g., ISP and other non-DoD networks) are blocking outbound ICMP messages. The following are exceptions are allowed outbound. Exceptions: ICMP messages Packet-too-Big (type 3, code 4) Source Quench (type 4) Echo Request (type 8) If ICMP messages are not blocked outbound, this is a finding. JUNOS Example: [edit interfaces] fe-2/0/10 { description "downstream link to our network”; unit 0 { family inet { filter { input egress-filter; } address 10.0.0.1/24; } } } } [edit firewall] family inet { filter egress-filter { term icmp-out-good { from { source-address { 10.0.0.0/24; } protocol icmp; icmp-type [ echo-request source-quench ]; } then { accept; } } term icmp-out-bad { from { protocol icmp; } then { syslog; discard; } } } }

Check Text ( C-12836r2_chk )

Review ACLs configured on network devices connected to untrusted networks (e.g., ISP and other non-DoD networks) are blocking outbound ICMP messages. The following are exceptions are allowed outbound.

Exceptions:
ICMP messages Packet-too-Big (type 3, code 4)
Source Quench (type 4)
Echo Request (type 8)

If ICMP messages are not blocked outbound, this is a finding.

JUNOS Example:
[edit interfaces]
fe-2/0/10 {
description "downstream link to our network”;
unit 0 {
family inet {
filter {
input egress-filter;
}
address 10.0.0.1/24;
}
}
}
}

[edit firewall]
family inet {
filter egress-filter {
term icmp-out-good {
from {
source-address {
10.0.0.0/24;
}
protocol icmp;
icmp-type [ echo-request source-quench ];
}
then {
accept;
}
}

term icmp-out-bad {
from {
protocol icmp;
}
then {
syslog;
discard;
}
}
}
}

Fix Text (F-44086r1_fix)
Configure ACLs on network devices to block outbound ICMP messages. Exceptions to this rule are listed below. Exceptions: ICMP messages Packet-too-Big (type 3, code 4) Source Quench (type 4) Echo Request (type 8)