Vincent Joubert, Five Years After Estonia's Cyber Attacks: Lessons Learned for NATO? (May 2012) (full-text).
In April 2007 a series of cyber attacks targeted Estonian information systems and telecommunication networks. Lasting twenty-two days, the attacks were directed at a range of servers (web, email, DNS) and routers. The 2007 attacks did not damage much of the Estonian information technology infrastructure. However, the attacks were a true wake-up call for NATO, offering a practical demonstration that cyber attacks could now cripple an entire nation dependent on IT networks.