ICMP information such as (1) netmask and (2) timestamp is allowed from arbitrary hosts.
descriptions.securescout.com/tc/11010
descriptions.securescout.com/tc/11011
kb.juniper.net/InfoCenter/index?page=content&id=JSA10705
kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1434
www.osvdb.org/95
exchange.xforce.ibmcloud.com/vulnerabilities/306
exchange.xforce.ibmcloud.com/vulnerabilities/322
kc.mcafee.com/corporate/index?page=content&id=SB10053