Details

If Network Time Protocol is not authenticated, an attacker can introduce a rogue NTP server. This rogue server can then be used to send incorrect time information to network devices, which will make log timestamps inaccurate and affect scheduled actions. NTP authentication is used to prevent this tampering by authenticating the time source.

Solution

Configure the Cisco router to authenticate NTP sources using authentication that is cryptographically based as shown in the example below.

RP/0/0/CPU0:R4#ntp authenticate
RP/0/0/CPU0:R4#ntp authentication-key 1 md5 xxxxxx
RP/0/0/CPU0:R4#ntp trusted-key
RP/0/0/CPU0:R4#ntp server x.x.x.x key 1
RP/0/0/CPU0:R4#ntp server y.y.y.y key 1

Supportive Information

The following resource is also helpful.

• https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XR_Router_Y21M04_STIG.zip

This security hardening control applies to the following category of controls within NIST 800-53: Identification and Authentication.This control applies to the following type of system Cisco.

References

• 800-53|IA-3(1)
• CAT|II
• CCI|CCI-001967
• Rule-ID|SV-216540r531088_rule
• STIG-ID|CISC-ND-001150
• STIG-Legacy|SV-105605
• STIG-Legacy|V-96467
• Vuln-ID|V-216540

Source

• Tenable.com/audits