Trojans are targeting your computers to mine bitcoins. I found report that they find it in the torrent application. I would lie to see if it can bring some significant amount of Bitcoins.
No they don't do that anymore. It used to be that some trojans would infect computers and secretly mine bitcoins without the owner knowing but those days are long gone. There would be no point mining bitcoins because even the best computers are no match for ASICs. This has been true since 2013.
As for the torrent application, what you are probably thinking about is uTorrent. The latest version of uTorrent added a program called Epic Scale that uses your CPU to perform computing tasks in the background while it is not in use - one of these tasks being cryptocurrency mining. The cryptocurrency in this case was not Bitcoin but a related coin called Litecoin. Installing Epic Scale was technically optional as you could choose to opt out during the installation process although the installer was written in a way that made it easy to overlook this option.
Can a bitcoin mining virus make a profit today? Actually, yes, it can. But it would make much more sense to channel the computing power into mining altcoins instead. I wrote a detailed analysis of how much profit 1 million infected computers can make
here which I've reposted below:
Assuming it could be written and not detected. It would pull either part of the cpu or part of the discrete gpu.
neither part does a lot of hashing. Say you bleed 10 percent of the cpu or gpu. maybe 50mh a pc so 20 pc's for 1 gh.
2000 pc's for 1th
2,000,000 pc's for 1ph.
not much more can be bleed off without detection.
So is it possible to make a virus that infects 2mill pc's sure. and if you are never caught you hash at 1ph. my guess is it would be found out quickly. since all the pc's would be dedicating a decent amount of cpu/gpu/watts to the mining.
If 20 PCs equal 1 GH/s then wouldn't you need 20,000 PCs for 1 TH/s and 20,000,000 PCs for 1 PH/s?
Anyway, both Bitcoin mining viruses and non-SHA-256 altcoin mining viruses would be profitable (it is free electricity, after all). A 1 million PC botnet where each PC is capable of 50 MH/s would have a total hashpower of about 50 million MH/s or 50 TH/s. At the current difficulty, the botnet operator would get a reasonable-ish passive profit of $150* per day according to
Coinwarz.
However, the botnet operator could earn much more than this if he chose to mine CPU and GPU mineable altcoins instead. If he mined Darkcoin and we assume that each PC has 3 MH/s of X11 hashing power, he would get $75,000** per day!
Viruses that mine scrypt-based currencies would fall somewhere in the middle as they have ASICs built for them but the performance difference between ASIC mining and GPU mining is not as extreme as SHA-256.
*If the miner only mined at 10% max performance to prevent the PC owners from finding out, it would only bring in $15 a day.
**Again, if the miner only mined at 10% max performance, it would bring in $7,500 a day. I'm not sure if this is practically feasible though since dumping that many coins on an exchange every single day would depress the price and surely the exchange owners will find out?