Why does Avast and other antivirus' detect gpu miners as viruses? For example I was downloading the latest cgminer and Avast blocked the download saying it was a virus. Is this true or is it a false positive? I've had other antimalware (I think Malwarebytes) detect cgminer as a virus.
This is probably because hackers install these miners on peoples computers without their knowledge or make a botnet of miners. 

Solution to this is placing your miner to ignore-list or get another antivirus like Avira, Avg, or just switch to linux and no need for antivirus anymore.