The Necurs botnet is a distributor of many pieces of malware, most notably Locky.
Reports
Around June 1, 2016, the botnet went offline, perhaps due to a glitch in the command and control server running Necurs. However, three weeks later, Jon French from AppRiver discovered a spike in spam emails, signifying either a temporary spike in the botnet's activity or return to its normal pre-June 1 state.[1][2]
In a 2020 report, it was noted to have particularly targeted India, Southeast Asia, Turkey and Mexico.[3]