If you are seeing queries for this domain, than you are likely participating in DNS Amplification attacks and your DNS server is probably reachable from the internet and has recursion enabled.
If you are seeing responses for this domain.. unlucky. You are currently beeing DDOS-ed! Good luck.
IPtables:
There are two iptable rules available. If your distribution supports Iptables 'u32' module pick this one, otherwise use the 'string' rule.
U32:
iptables --insert INPUT -p udp --dport 53 -m u32 --u32 "0x28&0xFFDFDFDF=0x03414d50 && 0x2c&0xFFDFDFDF=0x0a435241 && 0x30&0xDFDFFFDF=0x434b2d5a && 0x34&0xDFDFDFFF=0x4f4e4502 && 0x38&0xDFDFFF00=0x52550000" -j DROP -m comment --comment "DROP DNS Q amp.crack-zone.ru"
More U32 rules can be found here:
https://github.com/smurfmonitor/dns-iptables-rules/blob/master/domain-blacklist.txt
String:
iptables --insert INPUT -p udp --dport 53 -m string --from 40 --to 59 --algo bm --hex-string '|03616d700A637261636b2d7a6f6e6502727500|' -j DROP -m comment --comment "DROP DNS Q amp.crack-zone.ru"
More Iptables rules for the STRING module can be found here:
https://github.com/smurfmonitor/dns-iptables-rules/blob/master/domain-blacklist-string.txt
Source:
94.102.51.228
Name server:
;; ANSWER SECTION:
crack-zone.ru. 51518 IN NS jim.ns.cloudflare.com.
crack-zone.ru. 51518 IN NS fay.ns.cloudflare.com.
;; ADDITIONAL SECTION:
fay.ns.cloudflare.com. 72548 IN A 173.245.58.115
jim.ns.cloudflare.com. 85943 IN A 173.245.59.125
jim.ns.cloudflare.com. 85943 IN AAAA 2400:cb00:2049:1::adf5:3b7d
fay.ns.cloudflare.com. 72548 IN AAAA 2400:cb00:2049:1::adf5:3a73
Response:
TXT 3
Rsize 9226
Whois
% By submitting a query to RIPN's Whois Service
% you agree to abide by the following terms of use:
% http://www.ripn.net/about/servpol.html#3.2 (in Russian)
% http://www.ripn.net/about/en/servpol.html#3.2 (in English).
domain: CRACK-ZONE.RU
nserver: fay.ns.cloudflare.com.
nserver: jim.ns.cloudflare.com.
state: REGISTERED, DELEGATED, UNVERIFIED
person: Private Person
registrar: REGRU-REG-RIPN
admin-contact: http://www.reg.ru/whois/admin_contact
created: 2013.06.22
paid-till: 2014.06.22
free-date: 2014.07.23
source: TCI