NiceHash Miner is not a virus or malware.
Appart from 3rd party miners, we either created or used GPL open source software to build NiceHash Miner. We can guarantee you that software, built by us, does not contain any malware. However, we cannot guarantee that for 3rd party miners which are in your discretion to use or not. 3rd party miners are created and maintained by anonymous developers who charge developer fee for the use of the miner and these miners are not open source, therefore we cannot verify that the code is completely harmless.
Do note that we are actively developing our own mining solutions (project Excavator), which would eventually replace 3rd party miners.