I was using firmware from manufacturer since 2 months ago and it was totally ok untill I tried to add 3 more second hand M3 (seems they have infected my farm - ). these pools are not default ones ( default workers was microbt directing to f2pool )  and as  " efudd " mentioned this user (https://www.nicehash.com/miner/3CJgXokLQrRCQcEoftS7MbPDSXhXpX6P55)  on nicehash seems to be hijacker.

How can I clean this virus? Do you think if I unplug all of the miners from network and start updating their firmware with sd card will work ?