Weeks after the disclosure around the ProxyLogon group of security bugs, exploitation attempts against unpatched Microsoft Exchange servers have skyrocketed.

Derek Manky, Chief of Security Insights & Global Threat Alliances at Fortinet's FortiGuard Labs, said that last week researchers with FortiGuard Labs saw activity double over two days for cybercriminals targeting the vulnerabilities. The attackers are using the flaws to deploy cryptominers, ransomware (such as the recently discovered DearCry ransomware) and other malicious campaigns, he said.