The worst hacks of all time

In March 2013, European spam-prevention service Spamhaus was hit with the most powerful cyberattack in history, using more servers and bandwidth than any other attack in history. Speeds slowed for large sections of Europe, according to CloudFlare, a company hired by Spamhaus to thwart its attacks.

The attackers used nearly 100,000 servers to send 300 gigabits of traffic per second. That's more than three times larger than the Iranian-sponsored cyberattacks of September 2012, which prevented access to some U.S. banks' websites for days.