The ethminer is an Ethereum GPU mining worker. It origins in cpp-ethereum project (where GPU mining has been discontinued). Then hugely improved in Genoil's fork.
NOTICE: Antivirus programs may detect and warn that this is a coin miner, which is correct since this is exactly an Ethereum miner. Antivirus programs issue such warning because some individuals install miner software on compromised computers to mine for them. See the discussions in https://github.com/ethereum-mining/ethminer/issues?utf8=%E2%9C%93&q=is%3Aissue+virus.