Fifty-four zero-day vulnerabilities were discovered last year, more than double that of 2014. The number of mega-breaches of more than 10 million records also hit a record high. The most attractive zero-days for attackers are those in widely-used software such as Internet Explorer and Adobe Flash. The overall email spam rate last year was 53 percent, down from 60 percent in 2014 and 66 percent in 2013. However, the overall number of bots originating in China rose by 84 percent, as a result of increased broadband penetration.”]