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avast has no problems with torrent applications/downloads.
It will monitor and scan them.

But very often torrents are illegal and contain malware.

Keep in mind that the torrent protocol was designed to make downloads faster,
by downloading 1 file from several sources at the same time.
In theory it sounds nice, but it basically never worked as “advertised”.
In fact is almost always slower than downloading from the publisher’s server.
Bandwidth has increased a lot in a short time.