They're only attacking host-lookup, so you just have to worry about people who can connect to your service and are able to control name server response. This means your network services that are internet-accessible. Everything else can wait for a maintenance window for the reboot.

  ~# netstat -lnp | grep -e "\(tcp.*LISTEN\|udp\)" | cut -d / -f 2- | sort -u
  cupsd          
  dnsmasq        
  httpd          
  nmbd           
  ntpd           
  qemu-kvm       
  rpc.portmap    
  rpc.statd      
  sendmail: acce 
  smbd           
  ssh           
  sshd