NTP

Command to scan device to view NTP connection responeses.

ntpdc -c monlist <IP address>

Example of command and output

Command:

ntpdc -c monlist 146.6.177.21

Ouput:

remote address          port local address      count m ver rstr avgint  lstint
===============================================================================
ns1.utexas.edu           123 146.6.177.21       43244 4 4      0   1065       6
ns2.utexas.edu           123 146.6.177.21       43230 4 4      0   1065      62
security-scanner05.inf 61021 146.6.177.21           1 3 4      0    107     107
58.215.177.51          40205 146.6.177.21           1 3 4      0 1855107 1855107
matlock.infosec.utexas 57096 146.6.177.21           4 3 3      0 921718 1912102
cpe-173-174-33-58.aust 34854 146.6.177.21           4 3 4      0 481147 1924159
security-scanner142.in 43852 146.6.177.21           1 3 4      0 2212475 2212475
security-scanner113.in 56052 146.6.177.21           2 3 4      0 1444282 2887937
feederfish.infosec.ute 51834 146.6.177.21           7 3 4      0 696372 3045750

Note:  According to the ISO, the only remote addresses that connect to a device are ns1.utexas.edu and ns2.utexas.edu

For "standard" Linux distributions, devices should be configured as such below to restrict remote NTP address connections

edit /etc/inet/ntp.client -> ntp.conf

Added:

#added for DDoS prevention - don't allow any machine, except those w/o flags

restrict default notrust nomodify noquery
restrict 127.0.0.1
restrict 146.6.177.21
restrict 128.83.185.40
restrict 128.83.185.41
restrict 146.6.177.23
restrict 146.6.177.22
restrict 146.6.177.15
restrict 146.6.177.16
restrict 172.16.54.150
restrict 128.83.59.200

Note:  The IP addresses listed in the configuration file are