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The system must not respond to Internet Control Message Protocol (ICMP) timestamp requests sent to a broadcast address.


Overview

Finding ID Version Rule ID IA Controls Severity
V-22411 GEN003604 SV-45723r1_rule Medium
Description
The processing of (ICMP) timestamp requests increases the attack surface of the system. Responding to broadcast ICMP timestamp requests facilitates network mapping and provides a vector for amplification attacks.
STIG Date
SUSE Linux Enterprise Server v11 for System z 2016-12-20

Details

Check Text ( C-43090r1_chk )
Verify the system does not respond to ICMP TIMESTAMP_REQUESTs set to broadcast addresses.

Procedure:
# cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

If the result is not 1, this is a finding.

Note: The same parameter controls both ICMP ECHO_REQUESTs and TIMESTAMP_REQUESTs.
Fix Text (F-39121r1_fix)
Configure the system to not respond to ICMP TIMESTAMP_REQUESTs sent to broadcast addresses. Edit /etc/sysctl.conf and add a setting for "net.ipv4.icmp_echo_ignore_broadcasts=1" and reload the sysctls.

Procedure:
# echo "net.ipv4.icmp_echo_ignore_broadcasts=1" >> /etc/sysctl.conf
# sysctl -p