Maybe it is a DDos attack that they can't prevent.
Although distributed denial of service (DDoS) attacks have become a mainstay of arsenals of hackers, their profile has changed considerably in the past year or so,making them an even greater threat to companies. In fact, Forrester recently conducted a survey of 400 IT decision-makers where 74 percent of respondents reported experiencing one or more DDoS attacks in the past year-even though they had security measures in place to prevent such an attack.