All Linux servers are locked down to the highest security standards possible. All services are off by default and all ports shut. Only the required services started.
To lock down a server:-
On 28 of March 2013 the web's DNS was under attack by one of the largest DDoS attack in the web's history.
http://www.abc.net.au/news/2013-03-28/huge-cyber-attack-slows-internet-globally/4598574
The DNS is used by a web browser to translate a host name to a IP address, which is a bit like using a phone book to look up a person's phone number.
There are a number of ways of working around a DNS outage:-