Brute force attacks detection risks

I would like to ask if using brute force attacks on some websites or online services can be risky in any way for the hacker? Let's say that someone is using medusa tool to crack password on his account at some server. Is this visiable for administrators and risky somehow for the potential attacker? Or is it just seen as a milions tries to log in to the particular server and not as a threat? Can simple antivirus with firewall like lets say Avira detect this kind of penetration attempts? Do you actually think that anyone is looking at the login attempt logs or are they just ignored by the administrators or do they even exist on a regular server?